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The taxonomy of the family Linaceae has not been updated for over two decades and, particularly in Mexico, there is no work evaluating the taxonomic status of all its species. This study provides an update and integrates each of the taxa in the family Linaceae distributed in Mexico. Specimens of plants of this family collected from across the distribution range in Mexico and deposited in herbaria and digital databases, as well as specialized literature, were reviewed. Twenty-four native and one introduced species belonging to two genera, in addition to two varieties, were recognized for the family; the rate of endemism is more than 50% and all native species are under some threat. Reflecting the previously limited knowledge of the group, many of the specimens that we studied had been misidentified. We provide morphological descriptions, supplemented with photographs, illustrations, morphological descriptions, synonymy, ecological data, assessment of conservation status, and a key to differentiate these species. Results presented here reduce the number of native Linum species present in Mexico, modify the distribution range of others, provide data about conservation, as well as new records, and support the presence of the genus Hesperolinon in Mexican territory.

Linum schiedeanum Chamisso & Schlechtendal (1830a: 234). (Fig. 10b). Type:— MEXICO. Veracruz: in sylvaticis prope Jalapam, San Andrés, C. J. W. Schiede y F. Deppe 517 (C. J. W. Schiede s.n.) (holotype WU!, isotypes MO!, HAL!). Linum coulterianum Planchon (1848a: 498). Type:— MEXICO. Hidalgo: Zimapan, T. Coulter 758 (holotype K!, isotype GH!). Linum greggii Engelmann (1852a: 26). Cathartolinum coulterianum Small (1907d: 76). Cathartolinum schiedeanum (Schltdl. & Cham.) Small (1907d: 76). Cathartolinum greggii Small (1907e: 77). Type:— MEXICO. Coahuila: near Saltillo, Gregg 387 (holotype MO!, isotypes GH!, NY). Description: — Herbs, perennial, 10–70 cm in height, glabrous or almost glabrous, root thick; stems erect or extended, striate, unbranched to the inflorescence, glabrous. Leaves, basal ones entire, arranged in whorls of 4; distal ones ciliate, rarely opposite; oblanceolate to lanceolate, narrowly elliptical to obovate; 5.0–28.0 × 1.0–8.0 mm, sessile; apex acute, apiculate or mucronate; (1)3-nerved, midnerve conspicuous, occasionally also some lateral nerves; membranous, glabrous, or rarely with a few hairs near the base; stipular glands present at the base. Inflorescence a cymose panicle, pedicels 0.1–2.0 mm long; bracts 2.0–3.0 mm long, glabrous, margin glandular-dentate, apex acuminate, stipular glands absent; sepals persistent, lanceolate to ovate-lanceolate, 2.0–5.0 × 1.0– 1.5 mm; margin widely scariose, glandular-dentate; apex acute to cuspidate; 1–3-nerved, midnerve evident; stipular glands absent; petals yellow-green, oblanceolate or narrowly obcordate, 2.0–10.0 × 2.0–6.0 mm, sparsely pilose at the base; stamens 2.0–5.0 mm long; anthers 0.3–0.7 mm long, yellow; staminodia minute; styles free, 1.5–4.0 mm long; stigmata capitate, yellow. Fruit ovoid, light yellow, 1.4–5.0 × 3.0–4.0 mm, glabrous, pericarp thin, apex acute, dehiscent into 10 segments, false septa partially developed, septa with sparse marginal cilia; seeds ovate, reddish-brown, 1.0–2.0 × 0.6–1.0 mm. Distribution: — United States of America; in Mexico, in Chiapas, Mexico City, Coahuila, State of Mexico, Guanajuato, Hidalgo, Michoacan, Nayarit, Nuevo Leon, Oaxaca, Puebla, Queretaro, San Luis Potosi, Tamaulipas, Veracruz, and Zacatecas (Fig. 5b). Habitat and ecology: —Oyamel fir forest, deciduous forest, cypress-juniper forest, chaparral shrubland, crassirosette-leaved thorny shrublands, crop land, oak forests, oak-pine forests, thorny shrubland with lateral thorns, thornless or sub-thornless small-leaved shrublands, palm-tree forests, pine forests, grasslands, high or medium subdeciduous tropical forest, low deciduous forest, zacatonal alpine grasslands. Elevation 450–2950 m. Acrisol, Andosol, Cambisol, Kastanozem, Phaeozem, Fluvisol, Gleysol, Lithosol, Luvisol, Planosol, Regosol, Rendzina, Xerosol, and Vertisol soil types. Phenology: —Flowering and fruiting in June–February. Note: — Linum schiedeanum can be easily confused with L. nelsonii, since the latter varies in pubescence, size, and dimensions of leaves and flowers. However, among the characters that can be cited to differentiate L. schiedeanum include leaf width and glabrous pedicels and fruits. Conservation status: — Linum schiedeanum is a species with a wide distribution range and thrives in a great diversity of environments. According to the criterion and subcriteria B established by the IUCN (2019), this species can be considered as LC (EOO = 677,472.147 km 2 and AOO = 264 km 2,> 10 localities known). Specimens examined: — MEXICO. Chiapas: Amatenango, 5 km al este de la cabecera de Amatenango, 1676 m, 9 March 1988, J. López P. 339 (CHAPA!); Comitán, Al SW de Comitán atrás fraccionamiento Tenam, 1695 m, 16°15’17”N, 92°13’42”W, 4 September 2008, F. Hernández N. 2492 (XAL!); Oxchuc, 3 km S Rancho El Cura, 1970 m, 16°42’08”N, 92°15’52”W, S. Ochoa-Gaona et al. 4163 (CHAPA!); Oxchuc, Barrio Santisima Trinidad, 2050 m, 17 May 1988, F. Gómez S. 183 (MEXU!); San Juan Cancuc, Cruz ajk te´, 14 February 1992, J. Brett 824 (XAL!). Mexico City: Xochimilco, Xochitepec, 2250 m, 6 November 1977, A. Ventura A. 3150 (CIIDIR!, IBUG!). Coahuila: Artega, Puerto San Lorenzo, Cerro La Campana, 2460 m, 2 August 1979, L. Arce 10432 (ANSM!); Arteaga, Ejido El Puerto, 6 km de Los Lirios, 2520 m, 21 May 1980, R. López-Aguillón & J.A. Villarreal 664 (ANSM!, CHAP!); Arteaga, Ejido El Puerto, 2520 m, 27 May 1980, R. López A. & J.A. Villarreal 706 (ANSM!, CIIDIR!); Arteaga, Las Vigas Cañón de Jamé Sierra de Arteaga, 25°20’00”N, 100°39’00”W, 15 September 1988, J.A. Villarreal & M.A. Carranza 4581 (ANSM!); Arteaga, Las Vigas Cañón de la Carbonera, Sierra de Arteaga, 2600 m, 25°20’00”N, 100°39’00”W, 5 June 1987, J.A. Villarreal & M.A. Carranza 3758 (ANSM!); Arteaga, La Siberia Sierra de la Marta, 2300 m, 25°12’00”N, 100°30’00”, 27 May 1982, J.A. Villarreal 1656 (ANSM!); Arteaga, El Morro Sierra de Arteaga, 2900 m, 25°12’00”N, 100°16’00”, 25 September 1991, J.A. Villarreal & M.A. Carranza 6273 (ANSM!); Arteaga, Puerto San Lorenzo, Cerro La Campana, 2460 m, 2 August 1979, L. Arce s.n. (CHAPA!); Arteaga, Sierra de Zapalinamé, 2400 m, 27 June 1990, Hinton et al. 20411 (IEB!); Candela, Sierra Pájaros Azules Campo Santa María, 1800 m, 27°01’00”N, 100°50’00”W, 28 May 1997, P. Cruz A. 19 (ANSM!, CHAPA!); Candela, Sierra Pájaros Azules Campo Santa María, 1500 m, 27°02’00”N, 100°54’00”W, 5 December 1997, M.A. Carranza & D. Sánchez V. 2840 (ANSM!); Castaños, Sierra la Gavia Rancho La Gavia, 1500 m, 26°10’00”N, 101°18’00”W, 25 October 1995, J.A. Villarreal & M.A. Carranza 8362 (ANSM!); Castaños, Sierra la Gavia Rancho La Gavia, 1295 m, 26°10’00”N, 101°18’00”W, 10 August 1995, M.A. Carranza & J. Encinas 2262 (ANSM!); General Cepeda, Sierra Pilote de Fierro, 2950 m, 25°10’00”N, 101°25’00”W, 13 August 1993, M.A. Carranza et al. 1632 (ANSM!, CIIDIR!, MEXU!); Múzquiz, Río Sabinas al noroeste de Múzquiz, 453 m, 27°58’03”N, 101°34’28”W, 3 November 2005, J.A. Encina & I. Ramírez S. 1574 (ANSM!); Múzquiz, Carretera 53, Múzquiz-Boquillas, entrada al rancho la Babia, 980 m, 28°34’29”N, 102°03’27”W, 16 September 1999, J.A. Villarreal et al. 8866 (ANSM!); Múzquiz, Cañón Rincón de María en la Sierra de la Babia, 1450 m, 28°27’81.9”N, 102°04’50.7”W, 21 August 1999, M.A. Carranza et al. 3067 (ANSM!); Ocampo, Sierra Maderas del Carmen, 2270 m, 28°58’00”N, 102°35’00”W, 10 August 2004, D. Riskind et al. 23794 (ANSM!); Ocampo, Sierra del Pino, ejido Acebuches, 1850 m, 28°15’00”N, 102°59’00”W, 12 October 1991, M.A. Carranza et al. 901 (ANSM!, CIIDIR!, XAL!); Ocampo, Rancho La Cruz, 2000 m, 27°15’00”N, 102°40’00”W, 11 September 1991, M.A. Carranza & L. García S. 1176 (ANSM!, CIIDIR!, IBUG!); Ocampo, Sierra Maderas de Carmen, 2050 m, 28°59’00”N, 102°35’00”W, 31 July 1974, T. Wendt & A. Adamcewicz 443 (CHAPA!); Ocampo, 5 km al SW de Buenavista, 1650 m, 17 September 1981, J.L. Blando N. 8109145 (INEGI!); Escobedo, Las Vacas, 1600 m, 3 August 1958, C.A. Ely 195 (XAL!); Parras, Sierra de Parras en el arroyo seco del Rancho El Tunal, 2050 m, 1 September 1981, A. Rodríguez & P. Antonio H. 398 (ANSM!); Parras, Cañón de Gustrola, 1950 m, 25°20’00”N, 102°03’00”W, 14 October 1983, A. Rodríguez & M.A. Carranza 1259 (ANSM!, XAL!); Progreso, Rancho “Campo Santa María”de Cementos Mexicanos, 585 m, 27°05’38”N, 100°53’56”W, 4 November 2007, J.A. Encina & G. Rocha G. 2262 (ANSM!); Saltillo, Camino al Cerro El Penitente, 2710 m, 25°21’03”N, 100°54’47”W, J.A. Encina et al. 1488 (ANSM!); Saltillo, 300 m al oeste del Ejido Chapultepec, 2220 m snm, 25°14’40”N, 100°50’43”W, 6 July 2016, J.A. Encina et al. 5548 (ANSM!); Saltillo, Camino del Cuatro, Sierra de Zapalinamé, 1964 m, 25°21’58”N, 100°57’18”W, 19 March 2004, M.A. Llanas et al. 230 (CIIDIR!); Saltillo, Sierra de Zapalinamé, cañón de San Lorenzo, 2060 m, 25°23’00”N, 101°00’00”W, 03 August 1995, M.A. Carranza & J. Encinas 2229 (ANSM!, CIIDIR!, MEXU!); Saltillo, Sierra de Zapalinamé 3.15 km al noreste del ejido Cuauhtémoc, 2484 m, 25°17’33.48”N, 100°54’58.11”W, 30 August 2014, J.A. Encina et al. 4099 (ANSM!); Saltillo, Cañón de Timones al oeste de la Sierra de Zapalinamé, 2064 m, 25°19’47.36”N, 101°00’46.08”W, 26 April 2015, J.A. Encina & S. Guillermo R. 4554 (ANSM!); Saltillo, Sierra de Zapalinamé Cañón el Coyote, 2262 m, 25°21’28”N, 100°56’51”W, 19 August 2000, J.A. Encina et al. 575 (ANSM!); Saltillo, Camino del Cuatro Sierra de Zapalinamé, 1968 m, 27°58’03”N, 101°34’28”W, 1 November 2003, E. Padilla V. 1142 (ANSM!, MEXU!); Saltillo, Sierra de Zapalinamé Cañón de Santa Rosa-los Aguajes, 2400 m, 25°19’38”N, 100°57’46”W, 27 June 2000, J.A. Encina et al. 712 (ANSM!); Saltillo, Cañón de San Lorenzo, 1800 m, 13 September 1979, L. Arce & J.A. Villarreal 554 (ANSM!); Villa Acuña, Sierra del Carmen Canyon de Sentenela, 8 July 1936, F. Lyle W. & C.H. Mueller 583 (ANSM!); State of Mexico: Villa Nicolás Romero, Libertad, 2200 m, 10 September 1978, A. Ventura A. 3313 (INEGI!). Guanajuato: 3 km al W de Pozos, 2300 m, 28 June 1987, Rzedowski 43488 (XAL!). Hidalgo: Jacala, km 276 carretera México – Jacala, 1700 m, 30 October 1966, L.M.V. de Puga 15118 (IBUG!). Michoacan: Coalcomán, al S de Torrecillas, 1950 m, 18°48’25.66”N, 103°02’17.41”W, 21 December 1938, Hinton et al. 12805 (MEXU!). Nayarit: Xalisco, Cerro Boludo, al W de Xalisco, 1600 m, 20 February 1989, R.E. González & S. Aguilar 697 (UAMIZ!). Nuevo Leon: Aramberri, Puerto Carretas, 24 June 1981, O. Briones 714 (ANSM!); Dr. Arroyo, 7 km al S de La Encantada, 2520 m, 23°36’00”N, 99°50’00”W, 18 November 1993, J.A. Villarreal & M.A. Carranza 7681 (ANSM!); Santiago, Áreas cercanas a Cola de Caballo, 800 m, 25°23’00”N, 100°10’00”W, 10 October 1984, J.A. Villarreal et al. 2999 (ANSM!, XAL!); Santiago, Sierra Rancho Nuevo, 25°24’00”N, 100°28’00”W, M.A. Carranza et al. 1797 (ANSM!); Santiago, Laborcitas 15 km al oeste de V. de Santiago, 1400 m, 18 August 1976, V. Valdez T. 988 (INEGI!); Santiago, Cola de Caballo, 9 May 1979, J.A. Villareal 17217 (XAL!). Oaxaca: Ixtlán de Juárez, Carretera Ixtlán-Capulalpam km 7.1, 2000 m, 17°19’1.3”N, 96°26’5.59”W, 25 August 2002, S. Figueroa-Brito & F.Y. Guzmán-Rivera 139 (MEXU!). Puebla: Palmar de Bravo, Cerro Tepoxtla de San Martín Esperilla, 2500 m, 18°44’17.15”N, 97°32’23.49”W, 5 May 1992, P. Tenorio L. 18283 (MEXU!). Queretaro: Cadereyta, 5 km al S de Vizarrón, 2300 m, 16 August 1989, Rzedowski 48673 (CIIDIR!); Landa, 7 km al W de Tilaco, 1050 m, 9 June 1986, R. Fernández N. 3392 (IEB!); Landa, al N del parador Santa Martha, 1750 m, 30 November 1988, E. Carranza 1224 (IEB!); Landa, 1 km al Puerto de Malpaís, 1820 m, 13 June 1988, E. Carranza 588 (IEB!); Landa, 1 km al SW de El Lobo, 1600 m, 1 August 1987, Rzedowski 44023 (XAL!); Landa, 1 km al Sureste de El Pemoche, 1320 m, 2 May 1989, H. Rubio 626 (XAL!); 7 km por la brecha a Tres Lagunas y Valle de Guadalupe, 2000 m, 2 July 1987, H. Díaz-Barriga 3819 (IBUG!). San Luis Potosi: Guadalcázar, Matehualilla Sierra La Trinidad, 1920 m, 22°42’7.7”N, 100°28’44.1”W, 16 October 2005, O. Mares A. & M. Sosa M. 663 (ANSM!); Real de Catorce, Cerro La Cuchilla, 1920 m, 9 October 1979, J. García P. et al. 1309 (CHAPA!). Tamaulipas: Gómez Farias, Vecinity of “La Perra”, 1950 m, 18 June 1982, G. Diggs & M. Nee 2370 (XAL!). Veracruz: cerro al N del poblado de Jalcomulco, 19°20’40”N, 96°45’00”W, 20 November 1991. G. Castillo C & P. Moreno 7051 (XAL!); En el cerro, al N del poblado de Jalcomulco, 19°20’10”N, 96°44’50”W, 20 November 1991. G. Castillo C & P. Moreno 7448 (XAL!); Jalcomulco, 3 km antes de Jalcomulco por la Carr. Tuzamapa-Jalcomulco, 700 m, 19°22’00”N, 96°47’00”W, 15 January 1983, G. Castillo C. & A.P. Vovides 2765 (XAL!); Jalcomulco, Cerro del Brujo, 19°19’54”N, 96°45’42”W, 10 January 1992, G. Castillo C. & P. Zamora C. 8801 (XAL!); Jalcomulco, Cerro del Brujo, 19°19’54”N, 96°45’42”W, 10 January 1992, G. Castillo C. & P. Zamora C. 8789 (XAL!); Naolinco, Carr. Jalapa-Naolinco, 3 km antes de Naolinco, 1550 m, 29 June 1977, J.J. Fay & J.I. Calzada 729 (XAL!). Zacatecas: Susticacán, Sierra de los Cardos a 4 km al noroeste de la comunidad de Los Cuervos, 2230 m, 22°38’28.6”N, 103°11’53.6”W, 22 August 2019, L. Hurtado-Reveles 135 (CHAPA!)., Published as part of González-Velasco, Juan, Burgos-Hernández, Mireya, Galván-Escobedo, Iris G. & Castillo-Campos, Gonzalo, 2022, Taxonomic update of the flax family in Mexico, pp. 141-184 in Phytotaxa 549 (2) on pages 172-173, DOI: 10.11646/phytotaxa.549.2.3, http://zenodo.org/record/6622753, {"references":["Chamisso, L. K. A. & Schlechtendal, D. F. L. (1830 a) Linum schiedeanum. Linnaea 5: 234.","Planchon, J. (1848 a) Linum coulterianum. London Journal of Botany 7: 498.","Engelmann, G. (1852 a) Linum greggii, Linum rupestre var. cymolosum. Smithsonian Contributions to Knowledge 3: 26.","Small, J. K. (1907 d) Cathartolinum coulterianum, Cathartolinum rupestre, Cathartolinum schiedeanum, Cathartolinum wrightii. North American Flora 25: 76.","Small, J. K. (1907 e) Cathartolinum cruciate, Cathartolinum greggii. Cathartolinum muelleri, Cathartolinum tenellum. North American Flora 25: 77.","IUCN (2019) Guidelines for Using the IUCN Red List Categories and Criteria. Version 14. Prepared by the Standards and Petitions Subcommittee. Downloadable from: https: // www. iucnredlist. org / resources / redlistguidelines (accessed 22 April 2022)"]}

Linum nelsonii Rose (1906: 117) (Fig. 7c). Type:— MEXICO. Veracruz: municipality of Orizaba, Boca del Monte, E. W. Nelson 210 (Holotype: US!). Description: — Herbs, perennial, occasionally annual, 17–65 cm in height, glabrous or sparely pubescent, root thin; stems erect to decumbent, commonly unbranched up to the inflorescence, essentially glabrous. Leaves, basal entire or ciliated, arranged in whorls of 4–6; distal glandular-dentate, alternate or opposite, ovate to obovate; 4.0–18.0(– 21.0) × 2.0–12.0 mm, decreasing to the inflorescence, sessile, apex obtuse to rounded or acute in distal leaves; 3–5- nerved, central nerve prominent; smooth, glabrous or with scattered pubescence, stipular glands present at the base. Inflorescence a cymose panicle, pedicels 3.0–12.0 mm long, rarely pubescent, whitish hairs; bracts 3.5–10.0 mm long, margin denticulate, apex acuminate, stipular glands present at the base; sepals persistent, lanceolate to narrowly lanceolate or narrowly ovate, 2.5–4.0 × 1.0–2.0 mm, margin glandular-dentate, apex acute to acuminate; 1–(3)-nerved, central nerve prominent; sparsely pubescent, occasionally with stipular glands present at the base; petals yellow-green, oblanceolate to obovate, 3.0–5.0 mm long, glabrous; stamens 2.0–4.0 mm long, villous at the base; anthers 0.6–1.0 mm long, light yellow; staminodia small; styles free, 1.7–4.0 mm long; stigmata capitate, yellow. Fruit widely ovoid, yellow, 1.4–2.0 × 1.5–2.0 mm, pericarp thin, apex acute pubescent, dehiscent into 10 segments, false septa partially developed, septa occasionally with marginal cilia; seeds oblong to ovate, reddish-brown, 0.8–1.3 × 0.5–0.7 mm. Distribution: —In Mexico, in Chiapas, Coahuila, Guanajuato, Hidalgo, Nayarit, Nuevo Leon, Oaxaca, Puebla, Queretaro, San Luis Potosi, Tamaulipas, and Veracruz (Fig. 2b); to Guatemala, Honduras, and Nicaragua. Habitat and ecology: —Deciduous forest, cypress-juniper forest, oak forests, oak-pine forests, chaparral shrubland, mangrove forest, thorny shrubland, thornless or sub-thornless small-leaved shrubland, pine forests, low deciduous tropical forest, medium or low evergreen tropical forest. Elevation 550–2400 m.Andosol,Acrisol, Cambisol, Phaeozem, Lithosol, Luvisol, Regosol, Rendzina, Vertisol, and Xerosol soil types. Phenology: —Flowering in February–November; fruiting in April–November. Note: —According to Rzedowski & Calderón de Rzedowski (1994), the type locality is probably in the state of Puebla. Although L. nelsonii is frequently confused with L. schiedeanum, L. nelsonii can be consistently differentiated from the latter by its pubescent pedicels and stipular glands present at the base of bracts and occasionally in sepals. Conservation status: —Although according to the criterion B2 established by the IUCN (2019), L. nelsonii can be considered as endangered because of presenting an AOO of 80 km 2, its EOO (496,346.970 km 2) exceeds the value necessary for a threatened category. Therefore, this species is LC given its wide distribution and number of known localities inside and outside the country. Specimens examined: — MEXICO. Chiapas: Comitán, km17, carretera Comitán, 3 Lagunas, 1781 m, 16°17’39”N, 92°15’59”W, 2 September 2008, G. López V. 1230 (XAL!); Oxchuc, Tz´unun, a 3 km de la escuela por el lado sur, 2400 m, 13 March 1988, F. Gómez S. 19 (MEXU!); Oxchuc, 8 km al norte de Oxchuc, 2400 m, 12 May 1988, F. Gómez S. 164 (MEXU!). Coahuila: Castaños, Sierra La Gavia, 1295 m, 26°10’00”N, 101°18’00”W, 10 August 1995, M.A. Carranza y J. Encinas 2261 (ANSM!); Castaños, Sierra La Gavia, 1500 m, 26°10’00”N, 101°18’00”W, 25 October 1995, J.A. Villarreal & M.A. Carranza 8363 (ANSM!); Ramos Arizpe, Sierra de La Paila, 1600 m, 25°58’00”N, 101°32’00”W, 2 November 1988, J.A. Villarreal et al. 4739 (ANSM!). Guanajuato: San Luis de la Paz, La Ventana, cerca de Mesas de Jesús, 2000 m, 24 March 1990, E. Ventura & E. López 7837 (XAL!). Hidalgo: Molango, 5-6 km al N de Ismolintla, 1900 m, 20°46’37.23”N, 98°43’59.95”W, 27 April 1981, R. Hernández et al. 5893 (MEXU!). Nayarit: Tepíc, 5 km de la desviación al Rancho La Noria, 1500 m, 21°29’00”N, 104°59’00”W, J.I. Calzada et al. 19192 (XAL!). Puebla: Oriental, Zautla, 2000 m, 6 August 1986, F. Ventura A. 22272 (XAL!). Nuevo Leon: Galeana, Ca. 13 miles SW of Galeana, 2200 m, 24°43’00”N, 100°12’00”W, 10 September 1999, Henrickson & V. Heuvel 22472B (ANSM!); Santiago, Cola de Caballo, 9 May 1979, J.A. Villarreal 2463 (ANSM!). Oaxaca: Eloxotitlán de Flores Magón, Alrededores del Puente de Fierro, 1175 m, 18°09’11.8”N, 96°51’11.7”W, 9 March 2001, Munn-Estrada et al. 856 (TEX!). Queretaro: Arroyo Seco, 6 km al E de la Florida, 1260 m, 21°25’48”N, 99°42’06”W, 13 April 2007, S. Zamudio et al. 13698 (IEB!); Jalpan de Serra, 4-5 km al SE de San Juan de los Durán, 1850 m, 24 May 2012, E. Carranza G. 7670 (ANSM!); Jalpan de Serra, Cañada en la ladera O del Cerro Grande, 2110 m, 21°25’56”N, 99°08’46”W, 29 March 2012, G. Aguilar-Gutiérrez et al. 854 (IEB!, XAL!); Jalpan de Serra, 4-5 km al sur de La Parada, 1200 m, 18 December 1991, B. Servín 1481 (IEB!); Jalpan de Serra, 2-3 km al poniente de El Saucito, 900 m, 13 March 1991, B. Servín 882 (IEB!); Landa, 2 km al S de El Rincón, 900 m, 2 April 1987, Rzedowski 42916 (XAL!); Pinal de Amoles, 2 km al S de San Pedro Escanela, 1740 m, 22 February 1991, E. Carranza 3035 (IEB!); Pinal de Amoles, 1.5-2 km al W de San Pedro Escanela, 1780 m, 17 April 1990, E. Carranza 2438 (IEB!); Pinal de Amoles, Cerca de Huazmazontla, 1300 m, 12 March 1989, Rzedowski 48399 (XAL!). San Luis Potosi: El Naranjo, Vicinity El Salto above El Naranjo, 446 m, 22°35’11.79”N, 99°23’0.59”W, 1 April 1960, J.A. Duke 3675 (MEXU!). Sinaloa: Concordia, 4.5 km al SE de La Petaca, 1700 m, 12 February 2000, R. Vega-Aviña & J.A. Gutiérrez-García 10554 (MEXU!). Tamaulipas: Hidalgo, Into the Sierra 14.9 mi W of Hotel Santa Engracia, 570 m, 24°01’00”N, 99°34’00”W, 17 April 1988, G. Nesom 6339 (XAL!). Veracruz: Huiloapan, Cerro de San Cristóbal, 1300 m, 18°48’00”N, 97°03’00”W, 22 April 1982, J.I. Calzada 8592 (XAL!)., Published as part of González-Velasco, Juan, Burgos-Hernández, Mireya, Galván-Escobedo, Iris G. & Castillo-Campos, Gonzalo, 2022, Taxonomic update of the flax family in Mexico, pp. 141-184 in Phytotaxa 549 (2) on pages 160-161, DOI: 10.11646/phytotaxa.549.2.3, http://zenodo.org/record/6622753, {"references":["Rose, J. N. (1906) Linum longipes. Linum nelsonii. Contributions from the United States National Herbarium 10: 117.","Rzedowski, J. & Calderon de Rzedowski, G. (1994) Linaceae. In: Universidad Nacional Autonoma de Mexico (Ed.) Flora del Valle de Tehuacan-Cuicatlan. Fasciculo 5: 1 - 15. [ISBN: 968 - 36 - 3875 - 5]","IUCN (2019) Guidelines for Using the IUCN Red List Categories and Criteria. Version 14. Prepared by the Standards and Petitions Subcommittee. Downloadable from: https: // www. iucnredlist. org / resources / redlistguidelines (accessed 22 April 2022)"]}

Linum aristatum Engelmann (1848: 101). (Fig. 3a). Type:— MEXICO. Chihuahua: Near Carizal south of El Paso, Wislizenus 101 (holotype MO!, isotype GH!). Cathartolinum aristatum Small (1907a: 83). Mesynium aristatum (Engelm.) W.A.Weber (1984: 3). Description: — Herbs, annual, 10–45 cm in height, glabrous, main root thick; stems extended, ascending, rigid, broomshaped, striate, branched from the base, glabrous. Leaves entire, alternate; basal leaves sometimes opposite; linear, (4.8)5.0–20.0 × 0.3–1.1 mm, sessile; apex acute to acuminate, tip whitish to translucent; 1-nerved, membranous, glabrous; stipular glands present at the base, black. Inflorescence a cymose panicle, pedicels thin, 6.2–34.0 mm long; bracts 5.5–9.0 mm long, apex acuminate, margin glandular-dentate, stipular glands absent; sepals deciduous, linearlanceolate, scariose, 6.4–7.5 mm long, glandular-dentate, apex smoothly attenuated; 3-nerved, central nerve evident; without stipular glands; petals yellow to yellow-orange, obovate, 8–12 mm long, glabrous; stamens 5–7 mm long, glabrous; anthers elliptical, 0.7–1.1(1.2) mm long, yellow; staminodia absent; styles fused to near the apex, 4.5–7.0 mm long; stigmata capitate, yellow. Fruit ellipsoid, yellow, clearly longer than wide, 3.5–4.0 × 2.5–3.0 mm, glabrous, pericarp thin, apex obtuse, dehiscent into 5 segments; seeds elliptical, dark brown, 2.5–3.0 × 0.8–1.0 mm. Distribution: — United States of America; in Mexico, in Chihuahua, Coahuila, and Tamaulipas (Fig. 2a). Habitat and ecology: —Cypress-juniper forest, oak forests, oak-pine forests, thornless or sub-thornless smallleaved shrubland, grasslands, pine forests, vegetation of sandy arid deserts. Elevation (300) 1100–3100 m. Dry sandy soils of the Phaeozem, Lithosol, Luvisol, Regosol, Vertisol, and Xerosol types. Phenology: —Flowering in March–August; fruiting in August–November. Note: — Linum aristatum is easily distinguished from the rest of the species with dehiscence into 5 segments for having pale ellipsoid fruits and thin pericarp, in addition to narrow and smoothly attenuated sepals. Conservation status: —According to IUCN Red List Categories and Criteria (IUCN 2019), L. aristatum is EN (B1 + 2ab(iii)), with an EOO et al. 2014). Specimens examined: — MEXICO. Chihuahua: Along hiway 45, 112 miles N of Gallego, 1250 m, 18 July 1975, K.L.Wallace et al. 136 (ENCB!); Juárez, 4.8 miles S of Samalayuca, 1275 m, 31°18’00”N, 106°29’00”W, 19 August 1971, J. Henrickson 5780 (MEXU!); Juárez, 5 km N of Samalayuca, 1250 m, 31°24’30”N, 106°27’36”W, 28 October 1972, T.L. Wendt et al. 9922 (MEXU!). Coahuila: Gravelly mesas near Díaz, 742 m, 29°10’24.81”N, 101°36’0.97”W, 17 April 1900, C.G. Pringle 8312 (MEXU!). Tamaulipas: Nuevo Laredo, Sandy upland fourteen miles south of Nuevo Laredo, 141 m, 27°20’25.11”N, 99°36’19.33”W, 24 March 1944, N.T. Heard & F.A. Barkley 14604 (MEXU!)., Published as part of González-Velasco, Juan, Burgos-Hernández, Mireya, Galván-Escobedo, Iris G. & Castillo-Campos, Gonzalo, 2022, Taxonomic update of the flax family in Mexico, pp. 141-184 in Phytotaxa 549 (2) on page 147, DOI: 10.11646/phytotaxa.549.2.3, http://zenodo.org/record/6622753, {"references":["Engelmann, G. (1848) Linum aristatum. Memoir of a Tour to Northern Mexico 101.","Small, J. K. (1907 a) Cathartolinum aristatum. North American Flora 25: 83.","IUCN (2019) Guidelines for Using the IUCN Red List Categories and Criteria. Version 14. Prepared by the Standards and Petitions Subcommittee. Downloadable from: https: // www. iucnredlist. org / resources / redlistguidelines (accessed 22 April 2022)","Fernandez, J. A., Hafner, M. S., Hafner, D. J. & Cervantes, F. A. (2014) Conservation status of rodents of the families Geomyidae and Heteromyidae of Mexico. Revista Mexicana de Biodiversidad 85: 576 - 588. https: // doi. org / 10.7550 / rmb. 36710"]}

Linum scabrellum Planchon (1848d: 507). (Fig. 11). Type:— MEXICO. Hidalgo: Zimapán, T. Coulter 754 (holotype K!). Cathartolinum scabrellum Small (1907c: 74). Linum macradenium Brandegee (1911: 181). Type:— MEXICO, San Luis Potosi, Minas de San Rafael, Purpus 4923 (holotype UC!, isotype F, GH!, MO!, US). Description: — Herbs, perennial, up to 50 cm in height, pubescent to densely pubescent, root thick; stems erect, ascending, striate, branched from the base, sometimes simple, covered with rigid, whitish, conspicuous hairs. Leaves entire, occasionally with marginal glands in the upper leaves; basal leaves opposite, distal leaves alternate; linear, linearlanceolate, inferior leaves occasionally elliptical, 5.0–17.0 × 1.0– 3.5 mm, sessile, apex acute to acuminate, 1-nerved, coriaceous, pubescent; black stipular glands present at the base, very conspicuous. Inflorescence a cymose panicle, pedicels (5.9)10.0–20.0 mm long; bracts 2.5–7.1 mm long, pubescent along the central nerve, margin glandular-dentate, apex acuminate; black stipular glands present at the base, very conspicuous; sepals persistent, lanceolate to narrowly ovate, 2.5–5.5(6.0) × 1.0– 2.2 mm, margin glandular-dentate; apex acute to acuminate, occasionally with purple hues; 3-nerved, central nerve evident; stipular glands two, black, present at the base, very conspicuous; petals yellow-orange, oblanceolate, 4–10 mm long, pilose at the base; stamens 4–7 mm long, glabrous or sparsely pilose; anthers 0.4–1.2 mm long, yellow; staminodia minute, sometimes absent; styles free, 2.5–6.5 mm long; stigmata capitate, yellow. Fruit ovoid to subglobose, yellow, 2.5 × 2.5–4.0 mm, glabrous, pericarp thick, apex acute, dehiscent into 10 segments, false septa partially developed, septa ciliated; seeds elliptical to ovate, reddish-brown, 1.5–2.0 × 1.0 mm. Distribution:—Endemic to Mexico, in Aguascalientes, Guanajuato, Hidalgo, Nuevo Leon, Oaxaca, Puebla, Queretaro, San Luis Potosi, and Veracruz (Fig. 5c). Habitat and ecology: —Cypress-juniper forest, cardonal shrublands, chaparral shrubland, crassi-rosette-leaved thorny shrublands, oak forest, oak-pine forest, yucca shrublands, thorny shrubland, thornless or sub-thornless smallleaved shrubland, pine forests, grasslands, low deciduous tropical forest, low deciduous thorny tropical forest, sandy arid desert vegetation. Elevation 1400–2950 m. Cambisol, Kastanozem, Phaeozem, Fluvisol, Lithosol, Luvisol, Regosol, Rendzina, Vertisol, and Xerosol soil types. Phenology: —Flowering in March–December; fruiting in June–December. Note: —This is the only species in Mexico that is pubescent throughout all its vegetative parts, with no leaves in whorls and with free styles. It is morphologically similar to L. rupestre, but the latter is entirely glabrous. It was observed that the specimens of L. scabrellum collected in localities further north of its distribution range are slightly less densely pubescent than those from central and southern Mexico; it is possible that Rzedowski and Calderón de Rzedowski (1992) refer to this character when they describe these plants as “ cinereas ” (i.e. whitish-looking). Conservation status: — Linum scabrellum is a species with a wide distribution range and according to the criterion B and subcriteria established by the IUCN (2019), this species can be considered as LC (EOO = 186,173.234 km 2). However, taking into account its AOO of 140 km 2 and the expansion of mining and ranching activities in its distribution area (Salinas-Rodríguez 2015, De Nova et al. 2019), the species could see its populations threatened in the short term. Specimens examined: — MEXICO. Aguascalientes: Tepezalá, Extremo NE deArroyo Hondo, 2000m, 22°11’05”N, 102°11’13”W, 1 November 2007, G. García 5386 (IEB!); Tepezalá, 4 km al E de Tepezalá, 2247 m, 22°13’13.1”N, 102°08’6.1”W, 19 April 2013, G. García R. 6015 (INEGI!). Guanajuato: Atarjea, Puerto del Gallo, 8 km al Sureste de La Joya, 2100 m, 14 December 1988, E. Ventura & E. López 6501 (XAL!); San Luis de la Paz, 5 km al S de Pozos, 2100 m, 24 September 1994, Rzedowski 52586 (ANSM!, XAL!); San Luis de la Paz, cerca de El Pregón, 24 September 1994, Rzedowski 52569 (IEB!, XAL!); 3 km al W de Pozos, 2300 m, 28 June 1987, Rzedowski 43481 (XAL!). Hidalgo: Nicolás Flores, El Arenalito, 20°46’04”N, 99°68’56”W, 20 September 1995, V.H. López B. 134 (CHAP!, XAL!). Nuevo Leon: Aramberri, Cerro Grande, 2180 m, 19 October 1986, Hinton et al. 19106 (CHAPA!, CIIDIR!, IEB!); Dr. Arroyo, Carretera Matehuala-Dr. Arroyo aprox. 38 km, 17 June 1992, J.A. Villarreal & M.A. Carranza 6555 (ANSM!); Dr. Arroyo, Santa Gertrudis, nr., 1780 m, 16 March 1993, Hinton et al. 22707 (ANSM!); Dr. Arroyo, Camino a Agua Nueva, 2000 m, 23 June 1981, O. Briones 683 (ANSM!, XAL!); Galeana, Santa Gertrudis, 1700 m, 20 July 1993, Hinton et al. 23043 (IEB!); Mier y Noriega, West of Refugio de Cerros Blancos, 1825 m, 1 October 2001, Hinton et al. 27692 (ANSM!). Oaxaca: Cuicatlán, 6 km al N de Cuicatlán, 1750 m, 19August 1987. A. Salinas T. et al. 4323 (XAL!); 2 km al NE-E de Suchixtlahuaca, 2100 m, 17°43’00”N, 97°21’00”W, 6 June 1985, F. Chiang et al. 2519 (MEXU!, XAL!). Puebla: Cañada Otate, brecha a Hijaderoaria, 2121 m, 18°01’00”N, 97°20’00”W, 5 November 2001, P. Tenorio L. & L. Kelly 21561 (MEXU!); Hwy 28, N of Azumbilla (which is N of Tehuacan), 2375 m, 18°41’00”N, 97°24’20”W, 16 July 1991, Mayfield et al. 876 (MEXU!). Queretaro: Peña Miller, Ejido Maguey Verde, 2242 m, 21°05’21”N, 99°41’45”W, 13 October 2005, O. Mares A. & M. Sosa M. 497 (ANSM!); Cadereyta, Alrededores de Maconí, 1800 m, 10 November 1988, Rzedowski 47642 (ANSM!); Ezequiel Montes, Cerro La Caja frente a la Peña de Bernal, 2157 m, 20°44’38.2”N, 99°55’49.3”W, 24 September 2020, J. González-Velasco & P. Albarrán-González 20001 (CHAPA!); San Joaquín, Cañada La Culebra, 1600 m, 27 August 1978, S. Zamudio 3221 (CIIDIR!); 5 km al S de Vizarrón, 16 August 1989, Rzedowski 48673 (CIIDIR!); Cadereyta, Alrededores de Maconí, 1800 m, 10 November 1988, Rzedowski 47642 (IBUG!); San Joaquín, Cañada La Culebra, 1600 m, 27 August 1978, S. Zamudio R. 3221 (IBUG!, XAL!); Tequisquiapan, 3 km al W de Las Rosas, 2000 m, 8 September 1990, Rzedowski 49998 (XAL!); Ezequiel Montes, 7.5 km de Bernal, carretera a Tolimán, 2000 m, 20°46’22”N, 99°54’14”W, 11 October 2008, E. Carranza & I. Silva 7493 (IEB!); Peñamiller, Camargo, 1700 m, 12 June 1991, E. Ventura & E. López 9229 (IEB!); Ezequiel Montes, 7.5 km de Bernal, carretera a Tolimán, 2000 m, 20°46’22”N, 99°54’14”W, 11 October 2008, E. Carranza & I. Silva 7493 (UAMIZ!); Peñamiller, Camargo, 1700 m, 12 June 1991, E. Ventura & E. López 9229 (XAL). San Luis Potosi: Ahualulco, 9.7 km al W del entronque Ahualulco-Charcas, 2100 m, 10 October 1985, F. García-Pérez 2025 (ANSM!, INEGI!, SLPM!); Armadillo de los Infante, Sierra de Álvarez, 1800 m, 1 September 2012, F. García S. 8640 (ANSM!, SLPM!); Armadillo de los Infante, Camino a Tlaxcalilla a 200 m del cruce con la carretera con dirección a la mina, 1711 m, 22°16’0.67”N, 100°40’13.6”W, 10 September 2020, A. Villalvazo-Hernández & J. González-Velasco 44 (CHAPA!); Charcas, 6 km al E de Miguel Hidalgo, 23°12’00”N, 101°04’00”W, 7 July 1985, P. Tenorio L. & T.P. Ramamoorthy 9208 (MEXU!); Guadalcazár, Km 9 carretera a Guadalcazár, 1635 m, 22°37’19.3”N, 100°29’26”W, 11 September 2020, A. Villalvazo-Hernández & J. González-Velasco 49 (CHAPA!); Guadalcázar, 1.6 km al este de la carretera Matehuala-San Luis Potosí, 1609 m, 9 November 2019, V.W. Steinmann & M.M. Salinas-Rodríguez 8249 (CHAPA!); Guadalcázar, El Cañón Hondo, 12 km al NW de Guadalcázar, 22°36’58”N, 100°29’21”W, 16 November 1996, R. Torres C. 14852 (IEB!); Guadalcazár, El Cañón Hondo, 12 km al NW de Guadalcazár, 22°36’58”N, 100°29’21”W, 10 October 1996, R. Torres C. 14698 (IEB!); Real de Catorce, 18 km del entronque Matehuala-San Luis Potosí, 1850 m, 23°50’00”N, 101°05’00”W, 5 June 1990, J.A. Villarreal et al. 5734 (ANSM!, IBUG!); Real de Catorce, Camino a Real de Catorce sobre la loma que está antes de entrar al pueblo, 2537 m, 23°26’26.5”N, 100°48’59”W, 12 September 2020, A. Villalvazo-Hernández & J. González-Velasco 52 (CHAPA!); Real de Catorce, Parte alta del cerro Quemado, 2910 m, 23°40’21”N, 100°54’45”W, 25 August 2013, S. Zamudio R. 16411 (IEB!); Soledad Diez Gutiérrez, 5 km al NE de Laguna Seca, 2000 m, 30 August 1955, Rzedowski 6293 (SLPM!); Villa Guadalupe, Sierra del Catorce rumbo a los lomeríos, 1833 m, 23°26’26.5”N, 100°48’59.6”W, 12 September 2020, A. Villalvazo-Hernández & J. González-Velasco 51 (CHAPA!); Villa Juárez, Camino Guaxcamá-Buenavista con dirección a la mina, 1215 m, 22°15’49.6”N, 100°39’38”W, 11 September 2020, A. Villalvazo-Hernández & J. González-Velasco 45 (CHAPA!). Veracruz: Perote, ladera de cerro, 2400 m, 19°33’47.17”N, 97°13’47.17”W, 19 December 1998, G. Castillo-Campos 19095 (MEXU!)., Published as part of González-Velasco, Juan, Burgos-Hernández, Mireya, Galván-Escobedo, Iris G. & Castillo-Campos, Gonzalo, 2022, Taxonomic update of the flax family in Mexico, pp. 141-184 in Phytotaxa 549 (2) on pages 170-171, DOI: 10.11646/phytotaxa.549.2.3, http://zenodo.org/record/6622753, {"references":["Planchon, J. (1848 d) Linum scabrellum. London Journal of Botany 7: 507","Small, J. K. (1907 c) Cathartolinum catharticum. Cathartolinum pringlei. Cathartolinum scabrellum. North American Flora 25: 74.","Brandegee, T. S. (1911) Linum macradenium. University of California Publications in Botany 4: 181.","Rzedowski, J. & Calderon de Rzedowski, G. (1992) Linaceae. In: Rzedowki, J. & Calderon de Rzedowski, G. (Eds.) Flora del Bajio y de Regiones Adyacentes. Fasciculo 6: 1 - 22. [ISBN: 0188 - 5170]","IUCN (2019) Guidelines for Using the IUCN Red List Categories and Criteria. Version 14. Prepared by the Standards and Petitions Subcommittee. Downloadable from: https: // www. iucnredlist. org / resources / redlistguidelines (accessed 22 April 2022)","Salinas-Rodriguez, M. M. (2015) Conocimiento, manejo y conservacion de la diversidad floristica de la Sierra Madre Oriental, Mexico. Universidad Autonoma de Nuevo Leon. Mexico. PhD Thesis, pp. 242."]}

Linum cruciata Planchon (1848b: 499). (Fig. 3d) Type:— MEXICO. Nayarit: Tepic, Sinclair s.n. (holotype K!). Cathartolinum cruciata Small (1907e: 77). Linum gracilentum M.E. Jones (1929: 148). Type:— MEXICO. Nayarit: Tepic, M.E. Jones 22882 (isotypes GH, UC, US!). Description: — Herbs, perennial, 15–50 cm in height, essentially glabrous, root thin; stems decumbent toward the base, branched from the base, glabrous in the basal part; pilose in the distal part, near nodes and the inflorescence. Leaves, basal ones entire, arranged in whorles of 4; distal ones dentate, alternate, widely ovated or elliptical, 5.4–13.8 × (3.2) 3.3–8.3 mm, sessile or subsessile, petiole villous; apex obtuse to subacute, apiculate; 1-nerved, more evident on the abaxial surface; slightly scariose, glabrous, or sparsely pilose, stipular glands present at the base. Inflorescence a cymose panicle, with extended branches, pedicels villous, (1.5)3.0–6.0 mm long; bracts 1.9–4.3 mm long, margin dentate, with pedunculate glands, apex acute, stipular glands present, black; sepals persistent, lanceolate, sometimes quite narrow, (1.8)2.4–3.0 × 0.4–0.8 mm, margin with conspicuous glandular teeth, apex acute to subacuminate, 3- nerved, central nerve evident, glabrous; petals light yellow, 4.0–6.0 mm long, glabrous; stamens 3.0–4.0 mm long; anthers 0.7–1.2 mm long, light yellow; staminodia minute; styles free, 2.5–4.3 mm long; stigmata capitate, yellow. Fruit widely ovoid, yellow, (1.1)1.3–1.7 × 1.1–2.0 mm, sparsely pilose above the middle portion, pericarp thin, apex acute, dehiscent into 10 segments, false septa poorly developed; seeds widely ovate, brown, 0.8–0.9 × 0.7–0.8 mm. Distribution: —In Mexico, in Durango, Jalisco, Nayarit, Queretaro, Sinaloa, Sonora, and Tamaulipas (Fig. 5a). Habitat and ecology: —Deciduous forest, oak forests, oak-pine forests, pine forests, high evergreen tropical forests, low deciduous tropical forest, low thorny deciduous tropical forest, low subdeciduous tropical forest. Elevation 1300–1900 m. Cambisol, Lithosol, Regosol, Vertisol, and Xerosol soil types. Phenology:—Flowering and fruiting in March–July. Note: —Endemic to Mexico. It is the only species of the genus within its distribution area that has a combination of characters including leaves in whorls and sepals with conspicuous glandular teeth. In addition, L. cruciata presents free styles and short and villous pedicels, which allow differentiating it from L. longipes. Conservation status: —Although L. cruciata has an EOO of 315,975.629 km 2, its distribution is not continuous, affecting the extent of occurrence of this species. Based on an AOO of 28 km 2 and the number of localities known (Specimens examined: — MEXICO. Durango: Canelas, 1200 m al Norte de Canelas, 5 March 1986, M. Vizcarra 265 (CHAP!, CHAPA!, CIIDIR!, IBUG!, IEB!, MEXU!, UAMIZ!); Steep side canyons of the RíoTamazula, 1300 m, 20 March 1972, D.E. Breedlove 24527 (ENCB!). Jalisco: Autlán, Sierra de Manantlán, 1900 m, 19°32’00”N, 104°14’00”W, 23 March 1965, R. McVaugh 23219 (ENCB!). Nayarit: Tepíc, near Tepíc, 1588 m, 21°29’18.31”N, 104°56’0.16”W, 5 January 1892, E. Palmer 2013 (US!). Queretaro: Jalpan, a 5 km al SE de Jalpan, 1400 m, 1 May 1982, P. Tenorio & R. Hernández 316 (MEXU!). Sinaloa: Capadero, Sierra Tacuichamona, 12 february 1940, H.S. Gentry 5583, 5585 (MEXU!). Sonora: Alamos, Entre San Bernardino y Chinipas, 1250 m, 27°19.3’00”N, 108°44’00”W, 18 March 1992, G. Ferguson et al. s.n. (ARIZ!). Tamaulipas: 3 km al Sureste de Puerto Purificación, 2 June 1990, F. González M. et al. 17402 (MEXU!); 7 km al Sureste de Puerto Purificación, 6 June 1990, F. González M. et al. 17467 (MEXU!)., Published as part of González-Velasco, Juan, Burgos-Hernández, Mireya, Galván-Escobedo, Iris G. & Castillo-Campos, Gonzalo, 2022, Taxonomic update of the flax family in Mexico, pp. 141-184 in Phytotaxa 549 (2) on page 151, DOI: 10.11646/phytotaxa.549.2.3, http://zenodo.org/record/6622753, {"references":["Planchon, J. (1848 b) Linum cruciata. London Journal of Botany 7: 499.","Small, J. K. (1907 e) Cathartolinum cruciate, Cathartolinum greggii. Cathartolinum muelleri, Cathartolinum tenellum. North American Flora 25: 77.","Jones, M. E. (1929) Linum gracilentum. Contributions to Western Botany 15: 148."]}

Linum rzedowskii Arreguín (1985: 262). (Fig. 10a). Type:— MEXICO, State of Mexico: Llano Pinahua, approximately 8 km SW from Rio Frío, municipality of Ixtapaluca, 3200 m, in a clearing in the middle of the pine forest, J. Rzedowski 37285 (holotype ENCB!). Description: — Herbs, perennial, 15–25 cm in height, glabrous, root thick; stem creeping or prostrate, slightly striate, branched from the base, glabrous. Leaves entire, alternate, linear-lanceolate, (3.0–)4.6–5.5(–10.0) × (1.0–)1.1–1.3(– 2.0) mm, sessile, apex acuminate; 1–3-nerved, central nerve evident; coriaceous, glabrous, stipular glands absent. Inflorescence racemose, pedicels (4.5) 6.9–10.6 mm long, glabrous; bracts 2.1–4.2 mm long, margin entire, apex acute, stipular glands absent; sepals persistent, ovate, 3.0–4.0 × 2.0–3.0 mm, shorter than the capsule; margin white, scariose; apex acute; 1-3 nerved, barely evident lateral nerves; glabrous, stipular glands absent; petals blue, obovate, 6.0–8.0(11) mm long, glabrous; stamens 2.4–4.2 mm long; anthers 0.6–1.0 mm long, yellow; staminodia minute; styles free, 1.1–1.9 mm long; stigmata capitate, yellow. Fruit ovate, yellow, 5.0–6.0 × 4.0–5.0 mm, glabrous, pericarp thick, apex acute, dehiscent into 10 segments; septa ciliate; seeds elliptical, brown, 3.0–4.0 × 1.2–1.5 mm. Distribution: —Endemic to Mexico, in the State of Mexico (Fig. 5b). Habitat and ecology: —Grasslands, pine forests, low deciduous tropical forest. Elevation 3000–3500 m.Andosol, Cambisol, Phaeozem, Planosol, Regosol, and Vertisol soil types. Phenology: —Flowering and fruiting in July–August. Note: —This blue-flowered species occurs only in a small area of the State of Mexico; its distribution does not overlap that of L. lewisii. The creeping habit, the white margins of sepals, and the size of petals support an easy differentiation. Conservation status: —Although, according to the B1 criterion established by the IUCN, L. rzedowskii can be considered Critically Endangered (CN) (EOO = 24 km 2), due to its AOO of 24 km 2 and a number of known localities, together with the degradation of its habitat adjacent to the largest human population nuclei by deforestation and tourism (Pineda-Jaimes et al. 2009, CONABIO 2021), this species is considered EN (B1 + 2abc(iii)). Specimens examined: — MEXICO. State of Mexico: Chalco, Río Frío Estación Forestal Zoquiapan, 3500 m, 16 August 1974, E. García M. et al. 1256 (CHAPA!); Ixtapaluca, Estación Experimental de Investigación y Enseñanza de Zoquiapan 8 km al S de Río Frío, 3250 m, 04 July 1975, S.D. Koch 75289 (CHAP!, CHAPA!); Ixtapaluca, Estación Experimental de Investigación y Enseñanza de Zoquiapan 8 km al S de Río Frío, 3000 m, 28 August 1975, S.D. Koch & J. Magaña M. 75471 (CHAPA!); Ixtapaluca, Estación Experimental de Investigación y Enseñanza de Zoquiapan 8 km al S de Río Frío, 3200 m, 30 October 1975, S.D. Koch 75704 (CHAPA!); Ixtapaluca, Estación Experimental de Investigación y Enseñanza de Zoquiapan 8 km al S de Río Frío, 3200 m, 3 July 1978, R. Vega A. 229 (CHAPA!); Ixtapaluca, Llano Pinahua, 3250 m, 12 August 1980, Rzedowski 36790 (CIIDIR!, IEB!, SLPM!); Ixtapaluca, Llano Grande, 3000 m, 30/August/1983, E. Ventura V. 1295 (IEB!, XAL!); Ixtapaluca, Llano Tepochaico, 3350 m, 17/July/1983, Rzedowski 38109 (IEB!, XAL!); Ixtapaluca, Llano Grande, 3100 m, 3 July 1983, E. Ventura V. 1051 (UAMIZ!)., Published as part of González-Velasco, Juan, Burgos-Hernández, Mireya, Galván-Escobedo, Iris G. & Castillo-Campos, Gonzalo, 2022, Taxonomic update of the flax family in Mexico, pp. 141-184 in Phytotaxa 549 (2) on pages 169-170, DOI: 10.11646/phytotaxa.549.2.3, http://zenodo.org/record/6622753, {"references":["Arreguin, S. M. L. (1985) Una nueva especie de Linum (Linaceae) del Valle de Mexico. Phytologia 57: 261 - 266.","Pineda-Jaimes, N. B., Bosque-Sendra, J., Gomez-Delgado, M. & Plata-Rocha, W. (2009) Analisis de cambio del uso del suelo en el Estado de Mexico mediante sistemas de informacion geografica y tecnicas de regresion multivariantes: Una aproximacion a los procesos de deforestacion. Investigaciones Geograficas 69: 33 - 52.","CONABIO (2021) Indice de Impacto Humano en la Biodiversidad Terrestre. Comision Nacional para uso y conocimiento de la Biodiversidad. Available from: http: // geoportal. conabio. gob. mx / metadatos / doc / html / indihum 14 gw. html (accessed 1 December 2021)"]}

Linum berlandieri var. filifolium (Shinners) C.M. Rogers (1984a: 39). (Fig. 3c). Type:— UNITED STATES OF AMERICA. Texas: Brewster County, McVaugh 7798 (holotype SMU, isotypes F, GH!, MICH). Linum rigidum var. filifolium Shinners (1949: 136). Description: — Herbs, annual, occasionally perennial, 5–40 cm in height, hirsutulose near the base; root thin; stems erect, extended, ascending, striate, branching from the base, essentially glabrous, hirsutulose at the base. Leaves entire or distal leaves with few tiny marginal teeth, basal leaves opposite or alternate, distal leaves alternate; linear to linearlanceolate, (4.5)10.0–25.0 × (0.5)1.0–4.0 mm, the largest near or above the middle part of the stem; sessile, apex acuminate, 3-nerved, scariose, glabrous, stipular glands small present at the base. Inflorescence a cymose panicle, dense, pedicels 2.8–4.5 mm long, striate; bracts 3.8–6.3 mm long, margin with few minute teeth, apex acuminate, whitish, stipular glands at the base; sepals deciduous, lanceolate, (4.9)6.0–12.0 × 1.2–1.5 mm, margin with prominent glandular teeth, sometimes scariose; apex acute or attenuated, usually 3-nerved, glabrous, stipular glands absent; petals yellow-orange, reddish to brick-red below the middle portion, widely obovate, 11.0–19.0 mm long, glabrous; stamens 4.0–9.0 mm long; anthers 1.0–2.0 mm long, yellow; staminodia absent; styles fused to near the apex, 6.0–9.0 mm long, yellow; stigmata capitate, dark brown. Fruit widely ovoid to triangular-ovoid, yellow, 3.6–4.7 × 3.0–4.0 mm, pericarp thin, translucent, apex obtuse, dehiscent into 5 segments; seeds narrowly ovate, reddish-brown, 2.6–3.4 × 1.0– 1.6 mm. Distribution: — United States of America; in Mexico, in Chihuahua, Coahuila, and Nuevo Leon (Fig. 2a). Habitat and ecology: —Cypress-juniper forest, crassi-rosette-leaved thorny shrubland, oak forests, yucca forests, thornless or sub-thornless small-leaved shrubland, evergreen thorny tropical forest. Elevation 200–1750 m. Sandy, rocky soils, sometimes calcareous belonging to Kastanozem, Phaeozem, Lithosol, Planosol, Regosol, Rendzina, and Xerosol. Phenology:—Flowering and fruiting in March–June. Note: —Only this variety is distributed in Mexico. The presence of bracts with a whitish acuminate apex and the capsular fruit with thin, somewhat translucent pericarp, allows separating L. berlandieri var. filifolium from L. berlandieri var. berlandieri. Conservation status: —According to the criteria established by the IUCN (2019) and its distribution in a few northern states of Mexico, L. berlandieri var. filifolium is EN (B1 + 2ac(iii)) with an EOO Specimens examined: — MEXICO. Chihuahua: Manuel Benavides, Sierra Rica arroyo El Pedregoso, 1743 m, 29°10’12”N, 104°02’58”W, A. Juárez P. 165 (MEXU!, SLPM!). Coahuila: Villa Acuña, Serranias del Burro Rcho El Bonito, 29°01’30”N, 102°07’30”W, 4 May 1981, D.H. Riskind 2362 (ANSM!); 2.5 km of Rancho El Jardin on the road toward Mina El Popo, 1600 m, 29°07’00”N, 102°40’00”W, 28 July 1973, M.C. Johnston et al. 11840 (MEXU!); 5.2 rd miles NW of Rancho El Jardin towars Mina Popo, 1645 m, 29°09’00”N, 102°43’00”W, 2 July 1973, J. Henrickson & B. Prigge 11460 (MEXU!); 17 miles S of Allende along Hwy 57, 500 m, 28°12’00”N, 101°05’00”W, 3 May 1977, J. Henrickson & E. Lee 16025 (MEXU!); 22 km ESE of La Cuesta del Plomo on the Múzquiz-Boquillas highway, 1000 m, 28°38’38”N, 102°18’18”W, 7 June 1972, F. Chiang et al. 7543 (MEXU!); 52 miles SE of Big Bend National Park basin in the S end of the Sierra Maderas del Carmen in Cañon del Alamo, 1450 m, 28°52’00”N, 102°34’00”W, 5 August 1976, J. Henrickson & B. Prigge 14916 (MEXU!). Nuevo Leon: Hwy. 85, ca. 4 mi. SW of Nuevo Laredo, 14 November 1958, R.C. Rollins & R.M. Tryon 5802 (MEXU!)., Published as part of González-Velasco, Juan, Burgos-Hernández, Mireya, Galván-Escobedo, Iris G. & Castillo-Campos, Gonzalo, 2022, Taxonomic update of the flax family in Mexico, pp. 141-184 in Phytotaxa 549 (2) on pages 149-151, DOI: 10.11646/phytotaxa.549.2.3, http://zenodo.org/record/6622753, {"references":["Rogers, C. M. (1984 a) Linum berlandieri var. filifolium. North American Flora, series 2, 12: 39.","Shinners, L. H. (1949) Linum rigidum var. filifolium. Field & Laboratory 17: 136.","IUCN (2019) Guidelines for Using the IUCN Red List Categories and Criteria. Version 14. Prepared by the Standards and Petitions Subcommittee. Downloadable from: https: // www. iucnredlist. org / resources / redlistguidelines (accessed 22 April 2022)"]}

Linum tenellum Chamisso & Schlechtendal (1830b: 235). (Fig. 10c). Type:— MEXICO. Veracruz: Near Jalapa, C. J. W. Schiede & F. Deppe 518 (holotype HAL!, syntype HAL!, WU). Cathartolinum tenellum Small (1907e: 77). Description: — Herbs, annual, occasionally perennial, 8–50 cm in height, densely pubescent; hairs whitish, conspicuous; root thin; stems erect to decumbent, striate, commonly unbranched up to the inflorescence, pubescent. Leaves glandulardentate; basal leaves arranged in whorls of 4; distal leaves alternate, rarely opposite; elliptical to obovate toward the base, lanceolate to oblanceolate or oblong toward the distal part; 3.0–13.0 × (1.4)1.5–5.0 mm, gradually decreasing toward the inflorescence; sessile, apex acute to obtuse, 1-nerved; slightly membranous, pubescent; stipular glands present at the base. Inflorescence a cymose panicle, sparsely branched; pedicels 2.0–10.0 mm long; bracts 2.1–3.4 mm long, pubescent, margin glandular-dentate, apex acute, stipular glands present at the base of the lower bracts; sepals persistent, lanceolate to ovate, 1.9–3.0 × (0.8) 1.2–1.5 mm, margin glandular-dentate, apex acute, 3-nerved, pubescent or only along veins, stipular glands absent; petals yellow, obovate, 2.0–6.0 mm long, glabrous; stamens 2.0–3.0 mm long, sparsely pubescent at the base; anthers up to 1 mm long, light yellow; staminodia present, occasionally absent; styles free, 1.7–2.5 mm long; stigmata capitate, light yellow. Fruit ovoid, yellow with purple hues on the upper portion, 1.5–3.0 × 1.2–1.8 mm, sparsely pubescent, apex acute, puberulent or glabrous, dehiscent into 10 segments, false septa incompletely developed, septa without marginal cilia; seeds elliptical or ovate, brown, 1.0–1.2 × 0.5–0.7 mm. Distribution: —Endemic to Mexico, in Chiapas, Queretaro, San Luis Potosi, Tamaulipas, and Veracruz (Fig. 5a). Habitat and ecology: —Deciduous forest, oak forests, oak-pine forests, grasslands, and high or medium subevergreen tropical forest. Elevation 750–2200 m. Andosol, Cambisol, Phaeozem, Lithosol, Luvisol, Regosol, Vertisol, and Xerosol soil types. Phenology:—Flowering and fruiting in April–December. Note: — Linum tenellum is the only species in the genus that has leaves in whorls and that is densely pubescent throughout, with more stiff and conspicuous hairs, these being characters that support an accurate identification. Conservation status: —According to the IUCN criteria (IUCN 2019), L. tenellum is VU (B1 + 2ac(iii)). This species has an EOO of 6,180,759 km 2 and an AOO of 28 km 2, and is known from L. tenellum as a species in danger of extinction. Specimens examined: — MEXICO. Chiapas: La Independencia, Lake shore of Montebello, 1588 m, 16°06’16.81”N, 91°41’23.2”W, 2 May 1945, A.J. Sharp 45453 (MEXU!). Queretaro: Arroyo Seco, Aprox. 3 km de San Juan Buenaventura, 1460 m, 8 December 1988, E. Carranza 1236 (IEB!); Landa, 2 km al SO del Madroño, 1720 m, 8 May 1989, E. González 550 (IEB!, MEXU!). San Luis Potosi: Rioverde, Parque Nacional El Potosí, 2187 m, 1 March 2018, A.K. Gudiño-Cano et al. 646 (SLPM). Tamaulipas: Piedra Iman, 2 km al ESE de Sn. José, Sierra Sn. Carlos, 790 m, 24°40’30”N, 90°06’00”W, 22 November 1984, O. Briones 1245 (ANSM!). Veracruz: Atzalan, La Florida, 1700 m, 2 April 1976, F. Ventura A. 12609 (SLPM!, XAL!); Coacoatzintla, Coacoatzintla, 1200 m, 14 May 1973, F. Ventura A. 8294 (IEB!, XAL!); Miahuatlán, 5 km al SE de la Colonia Reforma, 1750 m, 19°43’00”N, 56°51’00”W, 24 April 1979, J.I. Calzada 5331 (XAL!); Tonayan, Desviación de Tonayán, 1600 m, 1 June 1981, M. Chazaro B. 156 (XAL!).

Linum elongatum (Small) H.J.P.Winkler (1931: 116). (Fig. 6a). Type:— UNITED STATES OF AMERICA. Texas: Laredo, Reverchon 3776 (originally cited as Bush 3776) (holotype NY!, isotypes MO, US!). Cathartolinum elongatum Small (1907f: 82). Description: — Herbs, annual, occasionally perennial, 15–30 cm in height, glabrous, root thick; stems erect to ascending, striate, branched from the base, branches diffuse, glabrous. Leaves entire, sometimes glandular, alternate, linear, 5.0–25.0 × 0.5–1.0(1.5) mm, sessile, apex acute; 1-nerved, nervation more evident in the abaxial surface, scariose; glabrous, stipular glands present, sometimes only at the base of distal leaves. Inflorescence a cymose panicle, pedicels 5.2–10.4 mm long; bracts 3.2–6.3 mm long, margin dentate, apex acuminate, with stipular glands present at the base; sepals deciduous, lanceolate, 6.0–11.0 × 1.4–1.8 mm, margin glandular-dentate, apex attenuate, 3-nerved, stipular glands absent; petals yellow-orange to salmon or brownish-red, wine-red base, widely obovate, 14.0–18.0 mm long; stamens 5.0–6.0 mm long; anthers 1.5–2.5 mm long, brick-red; staminodia absent; styles fused to near the apex, 7.0– 9.5 mm long; stigmata capitate, gray to wine-red. Fruit ovoid, yellow, 4.0–4.3 × 3.0– 3.7 mm, glabrous, pericarp thick, apex obtuse, dehiscent into 5 segments; seeds narrowly elliptical, reddish-brown, 2.3–3.0 × 1.2–1.3 mm. Distribution: — United States of America; in Mexico, in Tamaulipas (Fig. 5b). Habitat and ecology: —Thorny shrubland. Elevation 0–300 m. Compact sandy soils, Xerosol type. Phenology: —Flowering in February–May; fruiting in March–August. Note: —In its habitat, during the flowering period, the species is easily recognized due to the color of its petals with their distinctive wine-red-colored band near the center, brick-red anthers and wine-red to gray stigmata, which together provide diagnostic characters. The stems of the species are strongly striate. Conservation status: — Linum elongatum is known only from a narrow area of Texas and northern Mexico. One locality is known from Mexico, in the state of Tamaulipas, which may suggest some vulnerability. With only these data, it is not possible to carry out a conservation assessment. Therefore, to explore its probable threat category, it was necessary to integrate the records of GBIF. According to the B criterion (IUCN 2019), this species is Near Threatened (NT). Thus, it presents an EOO close to 20,000 km ² (22,940.563 km 2) and AOO Specimens examined: — MEXICO. Tamaulipas: Nuevo Laredo, Along Hwy 2, 5 mi E of junction with Hwy 85, 28 August 1976, C.M. Rogers 13477 (CIIDIR!)., Published as part of González-Velasco, Juan, Burgos-Hernández, Mireya, Galván-Escobedo, Iris G. & Castillo-Campos, Gonzalo, 2022, Taxonomic update of the flax family in Mexico, pp. 141-184 in Phytotaxa 549 (2) on pages 152-154, DOI: 10.11646/phytotaxa.549.2.3, http://zenodo.org/record/6622753, {"references":["Small, J. K. (1907 f) Cathartolinum elongatum. North American Flora 25: 82.","IUCN (2019) Guidelines for Using the IUCN Red List Categories and Criteria. Version 14. Prepared by the Standards and Petitions Subcommittee. Downloadable from: https: // www. iucnredlist. org / resources / redlistguidelines (accessed 22 April 2022)"]}

Key to Linaceae genera in Mexico 1. Petals with reddish venation, presence of basal adaxial appendages; carpels, styles, and stigmata 2 or 3; fruit dehiscent into 4 or 6 segments........................................................................................................................................................................ Hesperolinon - Petals without reddish venation, absence of basal daxial appendages; carpels, styles, and stigmata 5; fruit dehiscent into 5 or 10 segments.................................................................................................................................................................................... Linum, Published as part of González-Velasco, Juan, Burgos-Hernández, Mireya, Galván-Escobedo, Iris G. & Castillo-Campos, Gonzalo, 2022, Taxonomic update of the flax family in Mexico, pp. 141-184 in Phytotaxa 549 (2) on page 143, DOI: 10.11646/phytotaxa.549.2.3, http://zenodo.org/record/6622753

Linum Linnaeus (1753: 277). Type:— Linum usitatissimum L., N. Amer. Fl. 25: 67. 1907. Description:— Herbs, sometimes shrubs, annual or perennial; glabrous, puberulent, or pubescent partially or throughout; stems erect or extended, sometimes decumbent, unbranched or branched from the base or from the inflorescence, glabrous or pubescent. Leaves entire, dentate or glandular-dentate; alternate, opposite and/or in whorls; sessile or subsessile, with or without stipular glands. Inflorescence terminal, in cymose panicles or racemes, rarely in corymbs or solitary. Flowers with 5 sepals, imbricate, attached at the base, commonly persistent, rarely deciduous; entire, laciniate, ciliate, dentate, or glandular-dentate, glabrous or pilose; petals 5; yellow, white, pink, yellowishorange, orange, or blue, rarely red or crimson-brown; longer than sepals; stamens 5, provided with 5 small staminodia or absent; styles 5, free, connate at the base or fused up to 1/2 or more of the style length, filiform; stigmata capitate or straight; ovary superior, 5-locular or 10-locular for the presence of false septa. Fruit with septicidal capsule; ovoid, ellipsoid, or triangular-ovoid; dehiscent into 5 or 10 segments; glabrous or pilose; seeds 10, lenticular, flattened, elliptical to broadly elliptical; brown to reddish-brown; testa mucilaginous. The genus comprises 24 native and one introduced species distributed throughout the Mexican territory., Published as part of González-Velasco, Juan, Burgos-Hernández, Mireya, Galván-Escobedo, Iris G. & Castillo-Campos, Gonzalo, 2022, Taxonomic update of the flax family in Mexico, pp. 141-184 in Phytotaxa 549 (2) on page 146, DOI: 10.11646/phytotaxa.549.2.3, http://zenodo.org/record/6622753, {"references":["Linnaeus, C. (1753) Linum. Species Plantarum 1: 277."]}

Hesperolinon (A.Gray) Small, 1907h: 84. Type:— Hesperolinon californicum (Benth.) Small, N. Amer. Fl. 25: 86. 1907. Description: — Herbs, annual, thin, glabrous, occasionally pubescent or puberulent; stems erect or extended, sometimes slightly decumbent, not branched or branched from the base or from the inflorescence, glabrous or pubescent. Leaves entire or with marginal glands; basal leaves arranged in whorls of 4, distal leaves opposite or alternate; sessile or subsessile, with or without stipular glands. Inflorescence terminal, in a cymose panicle, sometimes condensed. Flowers with 5 sepals, imbricate, connate at the base, persistent, entire or with marginal glands, glabrous or villous; petals 5, yellow, white to pink, convolute, reddish venation; presence of basal adaxial appendages, more or less conspicuous, that sometimes expand into auricles; stamens 5, staminodia absent; styles 2–3, free, stigmata capitate or subcapitate; ovary superior, 2 or 3-locular, or 4 or 6-locular due to the presence of false septa. Fruit a septicidal capsule, ovoid, dehiscent into 4 or 6 segments, glabrous; seeds 4 or 6, triangular in cross-section, brown, often with darker spots; testa mucilaginous. The genus comprises one species in Mexico, distributed in a narrow area of the state of Baja California., Published as part of González-Velasco, Juan, Burgos-Hernández, Mireya, Galván-Escobedo, Iris G. & Castillo-Campos, Gonzalo, 2022, Taxonomic update of the flax family in Mexico, pp. 141-184 in Phytotaxa 549 (2) on page 143, DOI: 10.11646/phytotaxa.549.2.3, http://zenodo.org/record/6622753, {"references":["Small, J. K. (1907 h) Hesperolinon. North American Flora 25: 84."]}

Hesperolinon micranthum (A.Gray) Small, (1907i: 85.) (Fig. 1). Type:— UNITED STATES OF AMERICA. California: Mariposa County, Mt. Bullion, Bolander 4854 (holotype GH!, isotypes DS, UC!). Linum micranthum A. Gray (1868: 333). Description: — Herbs, 5–50 cm in height, glabrous to sparsely puberulent at the base; stems slightly decumbent, smooth, branched from the base, glabrous; stipular glands generally present at the base. Leaves entire, basal leaves in whorls, distal leaves alternate; linear or closely oblong, (5.5)10.0–20.0(–30.0) × (0.3)1.5–2.5(–3.0) mm; sessile, apex acute to obtuse, glabrous, stipular glands present only in basal leaves. Inflorescence in a cymose panicle, pedicels 3.9– 14.6(–30.0) mm long, sometimes longer in the fruit; bracts 0.9–1.3 mm long, margin entire, apex acute; sepals entire or with minute marginal glands, lanceolate, 1.0–3.0 × 0.6–0.9 mm, apex slightly acuminate, glabrous; petals white to light pink, oblanceolate, 1.5–3.5 mm long; stamens 1.5–2.5 mm long; anthers purple or dark purple, 0.3–1.0 mm long; styles 3, 0.5–1.0(–2.0) mm long, stigmata capitate; ovary 3 or 6-locular for the presence of false septa. Fruit yellow, 1.3–1.5 × 1.3–1.4 mm, pericarp thin, apex acute, dehiscent into 6 segments; seeds 6, 1.1–1.3 × 0.4–0.6 mm. Distribution: — United States of America; in Mexico, in northern Baja California (Fig. 2a). Habitat and ecology: — Cypress-juniper forest and chaparral shrubland. Elevation 50–2000 m. Common in serpentine soils in the California biogeographic province. Phenology: —Flowering and fruiting in May–October. Note: —Although the species is not endemic to Mexico, its distribution is restricted to the California biogeographic province (Delgadillo 1998, Morrone 2019). Hesperolinon micranthum is the only species in the genus reported (Springer 2009, Schneider et al. 2016, Jepson eflora 2019) and corroborated in this study, with a distribution range stretching to Mexico. According to the material reviewed, the species is clearly distinguished from the species in the genus Linum distributed in Mexico by the number of carpels, styles, and stigmata, as well as by the dehiscent fruit. Conservation status: —According to IUCN Red List Categories and Criteria (IUCN 2019), H. micranthum is Endangered (EN) (B1 + 2ac(iii)). Its extent of occurrence (EOO) is less than 5,000 km 2 (1,751.668 km 2) and its estimated area of occupancy (AOO) is 12 km 2. This species presents a restricted distribution, only known in Baja California in Mexico. Additionally, its habitat has been subjected to multiple anthropogenic pressures (Morrone 2019), and may face major risks. S pecimens examined: — MEXICO. Baja California: Ensenada, Rancho Caliente, 22 May 1971, I.L. Wiggins 21556 (ENCB!); Tecate, Cerro Jesús María, 770 m, 30°31’00’’N, 116°49’00’’W, 9 May 1970, R. Moran 17565 (ENCB!); Tecate, Cerro Matomí, 1300 m, 30°23’00’’N, 115°06’00’’W, 4 May 1973, R. Moran 20820 (ENCB!)., Published as part of González-Velasco, Juan, Burgos-Hernández, Mireya, Galván-Escobedo, Iris G. & Castillo-Campos, Gonzalo, 2022, Taxonomic update of the flax family in Mexico, pp. 141-184 in Phytotaxa 549 (2) on pages 143-146, DOI: 10.11646/phytotaxa.549.2.3, http://zenodo.org/record/6622753, {"references":["Gray, A. (1868) Linum micranthum. Proceedings of the American Academy of Arts and Sciences 7: 333.","Delgadillo, J. (1998) Floristica y Ecologia del Norte de Baja California. Universidad Autonoma de Baja California, Mexico, pp. 407. [ISBN: 968 - 73 - 2677 - 8]","Morrone, J. J. (2019) Regionalizacion biogeografica y evolucion biotica de Mexico: encrucijada de la biodiversidad del Nuevo Mundo. Revista Mexicana de Biodiversidad 90: e 902980.","Springer, Y. P. (2009) Do extreme environments provide a refuge from pathogens? A phylogenetic test using serpentine flax. American Journal of Botany 96: 2010 - 2021. https: // doi. org / 10.3732 / ajb. 0900047","Schneider, A. C., Freyman, W. A., Guilliams, C. M., Springer, Y. P. & Baldwin, B. G. (2016) Pleistocene radiation of the serpentine-adapted genus Hesperolinon and other divergence times in Linaceae (Malpighiales). American Journal of Botany 103: 221 - 232. https: // doi. org / 10.3732 / ajb. 1500379","IUCN (2019) Guidelines for Using the IUCN Red List Categories and Criteria. Version 14. Prepared by the Standards and Petitions Subcommittee. Downloadable from: https: // www. iucnredlist. org / resources / redlistguidelines (accessed 22 April 2022)"]}

Linum australe A. Heller (1898: 627). (Fig. 3b). Type:— UNITED STATES OF AMERICA. New Mexico: 4 mi E of Santa Fe, Heller & Heller 3724 (holotype NY!, isotypes F!, GH!, K!, KANU, KSC, MO!, MSC, NEB, US!). Cathartolinum australe Small (1907b: 81). Linum aristatum var. australe (A.Heller) Kearney & Peebles (1939: 485). Mesynium australe (A.Heller) W.A.Weber (1984: 3). Description:— Herbs, annual, 10–55 cm in height, puberulent in the basal part, glabrous or almost glabrous in the distal part; root thin; stems erect, striate, usually branched from the base, glaucous, puberulent. Leaves entire, sometimes slightly glandular-dentate, involute, alternate, linear, 4.0–20.0 × 0.5–2.0 mm, sessile, apex acute to acuminate, tip whitish, 1-nerved, coriaceous, glabrous, stipular glands present. Inflorescence a cymose panicle, pedicels 2.0–15.0 mm long, striate; bracts (3.9)4.0–6.0 mm long; margin scariose, glandular-dentate; sometimes with purple spots, apex acute, stipular glands present or sometimes absent; sepals deciduous, linear-lanceolate, 4.0–6.0 × (0.9)1.0– 1.5 mm, margin glandular-dentate, occasionally with reddish-purple spots, apex cuspidate-aristate, tip whitish, 1(–3)-nerved, stipular glands present or absent; petals light yellow to yellow-orange, oblanceolate or obovate, 6.0– 100 mm long, stamens 3.0–7.0 mm long; anthers 0.5–1.0(1.1) mm long, yellow; staminodia absent; styles fused to near the apex, 2.0–6.0 mm long, stigmata capitate. Fruit ovoid, yellow, 3.0–3.2 × 2.4–4.0 mm, glabrous, pericarp thick, apex obtuse, dehiscent into 5 segments; seeds elliptical, reddish-brown, 2.0–3.0 × 0.8–1.0 mm. Distribution: — United States of America; in Mexico, in Baja California, Chihuahua, Coahuila, and Durango (Fig. 2b). Habitat and ecology: —Oyamel fir forest, oak forests, oak-pine forests, thorny shrublands, and pine forests. Elevation 1500–2700 m. Montane soils, mainly Andosol, Cambisol, Phaeozem, Fluvisol, Lithosol, Regosol, Rendzina, Vertisol, Xerosol, and Yermosol. Phenology: —Flowering and fruiting in August–September. Note: — Linum australe is the only species within its distribution range that is glabrous beyond the base, with yellow flowers and fused styles almost to the apex. The stems and pedicels strongly striated to sulcate in the distal part are a distinctive character of the species. Its distribution in the northern part overlaps with the distribution of L. aristatum; however, they can be differentiated, since the latter presents a much more branched habit, a glabrous stem, and an ellipsoid fruit with thin pericarp. Conservation status: —According to the criteria established by the IUCN (2019) this species is EN (B2ac(iii)) with an EOO of 512,558.866 km 2 and AOO of 16 km 2, and Specimens examined: — MEXICO. Baja California: Sierra San Pedro Mártir, canyon at base of Cerro Botella Azul, 2700 m, 19 July 1988, S. Boyd & A. Liston 2700 (MEXU!). Chihuahua: Road between Babicora and Yepomera, 2500 m, 8 April 1977, Bennett et al. 821 (CHAPA!). Coahuila: Acuña, 75 km al noroeste de Ciudad Acuña, 565 m, 29°34’56”N, 101°43’31”W, 29 May 2016, J. A. Encina et al. 5415 (ANSM!). Durango: Súchil, Hacienda El Mortero, 1970 m, 15 September 2001, N. Almaraz et al. 60 (CIIDIR!)., Published as part of González-Velasco, Juan, Burgos-Hernández, Mireya, Galván-Escobedo, Iris G. & Castillo-Campos, Gonzalo, 2022, Taxonomic update of the flax family in Mexico, pp. 141-184 in Phytotaxa 549 (2) on pages 147-149, DOI: 10.11646/phytotaxa.549.2.3, http://zenodo.org/record/6622753, {"references":["Heller, A. A. (1898) Linum australe. Bulletin of the Torrey Botanical Club 25: 627. https: // doi. org / 10.2307 / 2478298","Small, J. K. (1907 b) Cathartolinum australe. North American Flora 25: 81.","Kearney, T. H. & Peebles, R. H. (1939) Linum aristatum var. australe. Journal of the Washington Academy of Sciences 29: 485.","IUCN (2019) Guidelines for Using the IUCN Red List Categories and Criteria. Version 14. Prepared by the Standards and Petitions Subcommittee. Downloadable from: https: // www. iucnredlist. org / resources / redlistguidelines (accessed 22 April 2022)"]}

Linum lewisii Pursh (1813: 210). (Fig. 6d). Type:— UNITED STATES OF AMERICA. Missouri: In the valleys of the Rocky Mountains and on the banks, M. Lewis s.n. (holotype PH!). Linum sibiricum var. lewisii (Pursh) Lindley (1828: 1163). Linum perenne var. lewisii (Pursh) Eaton & C.Wright (1840: 302). Linum perenne subsp. lewisii (Pursh) Hultén (1947: 1122). Adenolinum lewisii (Pursh) Á.Löve & D. Löve (1982: 348). Description: — Herbs, perennial, 5–80 cm in height, glabrous or nearly glabrous, root thick; stems erect, ascending, striate, branched near the base, glabrous. Leaves entire, alternate, linear to linear-lanceolate or linear-oblanceolate, 5.0–30.0 × 0.7–2.0(–4.5) mm, sessile, apex acute, 1-nerved, rough, glabrous, stipular glands absent. Inflorescence a cymose panicle, pedicels sparsely villous, 5.0–16.5(–20) mm long; bracts 3.2–6.4(8.0) mm long, margin entire, apex acute; sepals persistent, elliptical to elliptical-ovate, 2.6–5.0 × 1.8–3.7 mm; margin entire, scariose, whitish; apex acute; 1–3-nerved, stipular glands absent; petals blue, obovate, 6.0–15.0(–23.0) mm long; stamens 3.0–10.0 mm in length; anthers 1.0–1.7(–2.2) mm long, white; staminodia present, thin; styles free, 1.5–6.5(–12.0) mm long; stigmata capitate, light yellow. Fruit widely ovate, yellow, 4.6–7.0 × 4.4–6.8 mm, glabrous, pericarp thick, apex acute to apiculate, dehiscent into 10 segments; false septa partially developed, ciliate; seeds lanceolate-ovate, dark brown, 2.5–4.5 × 1.5–3.0 mm. Distribution: — United States of America; in Mexico, in Baja California, Chihuahua, Coahuila, Durango, Nuevo Leon, San Luis Potosi, Sonora, and Tamaulipas (Fig. 5a). Habitat and ecology: —Oyamel fir forest, cypress-juniper forest, crassi-rosette-leaved thorny shrublands, oak forests, yucca forests, thornless or sub-thornless small-leaved shrubland, grasslands, pine forests, low evergreen thorny tropical forest, deciduous forest, and thorny shrubland. Elevation 1500–3700 m. Cambisol, Kastanozem, Phaeozem, Lithosol, Luvisol, Planosol, Regosol, Rendzina, Vertisol, and Xerosol soil types. Phenology:—Flowering and fruiting in April–October. Note: — Linum lewisii can be confused with L. usitatissimum; however, the sepals shorter than the fruit with scariose whitish margins, a smaller bearing, and the capitate stigmata differentiate L. lewisii from the latter. Conservation status: —Although the AOO of this species is 76 km 2, the EOO (237,518.364 km 2) along with other subcriteria (IUCN 2019), such as a large number of environments where it occurs and the number of known localities inside and outside the country, make it possible to catalog L. lewisii as Least Concern (LC). Specimens examined: — MEXICO. Baja California: San Pedro Martír, Sierra de San Pedro Martír, 2560 m, 30°58’00”N, 115°25’00”W, 19 June 1985, R.F. Thorne et al. 60925 (MEXU!). Chihuahua: Madera, Colonia Chuhuichupa, 2240 m, 24 June 1990, A. Benítez 1382 (ANSM!, CHAP!, CIIDIR!, IEB!, UAMIZ!); Madera, Rancho La Ciénega, 2500 m, 31 August 1990, O. Bravo B. 1391 (CHAP!, CIIDIR!, UAMIZ!). Coahuila: Arteaga, Las Vigas Sierra de Arteaga, 2600 m, 25°20’00”N, 100°39’00”W, J.A. Villarreal & M.A. Carranza 3784 (ANSM!, CIIDIR!); Arteaga, Sierra de Los Lirios, 3600 m, 3 July 1943, E. Lyonnet 4003 (CHAP!, IEB!); Cerro San Pedro near N.L., 2200 m, 24°46’00”N, 100°47’30”W, 22 August 1974, T. Wendt et al. 627 (CHAPA!); Cima de Sierra La Marta, 3600 m, 25 October 1984, McDonald & Gómez 1247 (XAL!); Cima de Sierra La Viga, 3300 m, 25 October 1984, McDonald & Gómez 1211 (XAL!); Ramos Arizpe, Cañon del Carmen, 1400 m, 25°59’10”N, 101°28’30”W, 5 August 1975, M.F. Robert & J. Passini 4498 (ANSM!); Ramos Arizpe, Sierra de La Paila, 2000 m, 25°58’00”N, 100°25’00”W, 31 October 1987, J.A. Villarreal et al. 4156 (ANSM!); Ramos Arizpe, Cañon Loma Prieta, 1600 m, 25°51’00”N, 101°30’00”W, 23 October 1985, J.A. Villarreal et al. 3110 (ANSM!); Saltillo, Carretera 54 a 1 km al S de Guadalupe Victoria, 1950 m, 24°59’53”N, 101°04’84”W, 25 September 2013, F. Meraz et al. 108 (CIIDIR!); Saltillo. Sierra La Viga, 3700 m, 22 August 1986, McDonald 2087 (XAL!); Sierra Coahuilon, 3500 m, 18 June 1985, McDonald 1512 (XAL!); Sierra Coahuilon, 2500 m, 22 July 1985, McDonald 1725 (XAL!); Sierra de la Marta, 3580 m, 16 June 1985, McDonald 1433 (IBUG!, XAL!); Sierra Maderas del Carmen, 2250 m, 28°59’00”N, 102°36’30”W, 3 August 1974, T. Wendt & A. Adamcewicz 458 (CHAPA!). Durango: Pueblo Nuevo, El Salto, 2650 m, 23°47’26.2”N, 105°23’48.9”W, 1 September 1934, F.E. Pennel 18563 (MEXU!). Nuevo Leon: Cerro del Potosí, 3650 m, 21 June 1985, McDonald 1550 (XAL!); Cumbre de Cerro Potosí, 3600 m, 26 July 1985, McDonald 1780 (XAL!); Galeana, Cerro del Potosí, 3500 m, 16 May 1981, L. Arce et al. 1333 (ANSM!); Galeana, Rancho El Compromiso, 1600 m, 3 August 1999, E. Estrada C. 10553 (ANSM!); Galeana, Rancho Aguililla, 1885 m, 29 June 2000, Hinton et al. 27593 (ANSM!); Galeana, Cima del Cerro Potosí, 3670 m, 3 August 1988, A. García 61 (CHAP!, CIIDIR!); Galeana, Rancho Aguililla, 1850 m, 8 August 1990, Hinton et al. 20476 (CHAPA!); Galeana, Cima del Cerro Potosí, 3500 m, 4 August 1988, A. García 74 (CIIDIR!). San Luis Potosi: Charcas, Sierra de Monte Grande, 2300 m, 14 September 1989, J.A. Reyes A. 430 (CHAPA!). Sonora: Agua Prieta, Rancho Puerta Blanca (Cuenca Los Ajos Reserve), 1295 m, 31°18’57”N. 109°05’35”W, 23 March 2007, A.L. Reina & T.R. Van Devender 275 (MEXU!). Tamaulipas: Peña Nevada, 3600 m, 5 July 1985, McDonald 1618 (XAL!)., Published as part of González-Velasco, Juan, Burgos-Hernández, Mireya, Galván-Escobedo, Iris G. & Castillo-Campos, Gonzalo, 2022, Taxonomic update of the flax family in Mexico, pp. 141-184 in Phytotaxa 549 (2) on pages 155-156, DOI: 10.11646/phytotaxa.549.2.3, http://zenodo.org/record/6622753, {"references":["Pursh, F. T. (1813) Linum lewisii. Flora Americae Septentrionalis 1: 210.","Lindley, J. (1828) Linum sibiricum var. lewisii. Botanical Register 14: 1163.","Hulten, O. E. G. (1947) Linum perenne subsp. Lewisii. Flora of Alaska and Yukon 7: 1122.","Love, A. & Love, D. B. M. (1982) Adenolinum lewisii. Taxon 31: 348. https: // doi. org / 10.1002 / j. 1996 - 8175.1982. tb 03587. x","IUCN (2019) Guidelines for Using the IUCN Red List Categories and Criteria. Version 14. Prepared by the Standards and Petitions Subcommittee. Downloadable from: https: // www. iucnredlist. org / resources / redlistguidelines (accessed 22 April 2022)"]}

Linum australe var. glandulosum C.M. Rogers (1964a: 336). (Fig. 4). Type:— MEXICO. Durango: Otinapa, Palmer 465 (holotype US!, isotypes F!, GH, MO!, NY!). Mesynium australe (C.M. Rogers) W.A.Weber (1984: 3). Description:— Herbs with black stipular glands, very prominent on nodes, base of all leaves, bracts, and sepals. Distribution: — United States of America; in Mexico, in Chihuahua, Mexico City, Durango, State of Mexico, Guanajuato, Puebla, Sonora, and Veracruz (Fig. 2b). Habitat and ecology: —Cypress-juniper forest, oak-pine forests, prickly-pear cactus patches, grasslands, oak forests, thornless small-leaved shrubland, and pine forests. Elevation 1500–2650 m. Montane soils, mainly red-ash Acrisol, Andosol, Cambisol, Phaeozem, Lithosol, Luvisol, and Regosol. Phenology: —Flowering and fruiting in May–September. Taxonomic note: —The black and prominent stipular glands of L. australe var. glandulosum on the nodes, leaves, bracts, and sepals make it possible to clearly differentiate this variety of the species. Conservation status: — Rzedowski & Calderón de Rzedowski (1992) mention that L. australe var. glandulosum is at risk of extinction. However, according to the criteria established by the IUCN (2019) this variety is Vulnerable (VU) (B2abc(iii)), with an EOO of 164,257.374 km 2 and AOO of 28 km 2, known to Specimens examined: — MEXICO. Chihuahua: Chuhuichupa, near Chuhuichupa, 2148 m, 29°36’36”N, 108°22’48”W, 1 August 1936, H. LeSueur 132 (MO!). Mexico City: Milpa Alta, Paraje de Cuauhte, 2650 m, 4 July 1976, A. Ventura A. 1727 (IEB!). Durango: Durango, 18 miles west of Durango, 24 July 1964, C.M. Rogers 13183 (MEXU!). State of Mexico: Ixtapaluca, Cerro del Pino, 2300 m, 1 November 1972, M.L. Arreguín 346 (MEXU!); Tlalmanalco, Tramo Tlalmanalco-Amecameca, 2260 m, 12 September 1976, J. García P. 199 (CHAPA!). Guanajuato: León, 41 km al NE de León, 2450 m, 14 July 1987, J. Rzedowski 43752 (IEB!). Puebla: Acatzingo, San Juan Ocozoc, 2110 m, 18°59’00”N, 97°47’00”W, 1 July 1907, G. Arsené 1921 (MEXU!). Sonora: Yecora, 0.2 km north of Yecora and road to Agua Blanca, 1540 m, 28°22’46”N, 108°55’37”W, 15 July 1997, A.L. Reina et al. 780 (MEXU!). Veracruz: Perote, Sierra entre Mastaloyan y Frijol Colorado, 2650 m, 19°38’00”N, 97°23’00”W, 25 August 1984, G. Castillo C. et al. 3288 (XAL!)., Published as part of González-Velasco, Juan, Burgos-Hernández, Mireya, Galván-Escobedo, Iris G. & Castillo-Campos, Gonzalo, 2022, Taxonomic update of the flax family in Mexico, pp. 141-184 in Phytotaxa 549 (2) on page 149, DOI: 10.11646/phytotaxa.549.2.3, http://zenodo.org/record/6622753, {"references":["Rogers, C. M. (1964 a) Linum australe var. glandulosum. Sida 1: 336.","Rzedowski, J. & Calderon de Rzedowski, G. (1992) Linaceae. In: Rzedowki, J. & Calderon de Rzedowski, G. (Eds.) Flora del Bajio y de Regiones Adyacentes. Fasciculo 6: 1 - 22. [ISBN: 0188 - 5170]","IUCN (2019) Guidelines for Using the IUCN Red List Categories and Criteria. Version 14. Prepared by the Standards and Petitions Subcommittee. Downloadable from: https: // www. iucnredlist. org / resources / redlistguidelines (accessed 22 April 2022)","CONABIO (2021) Indice de Impacto Humano en la Biodiversidad Terrestre. Comision Nacional para uso y conocimiento de la Biodiversidad. Available from: http: // geoportal. conabio. gob. mx / metadatos / doc / html / indihum 14 gw. html (accessed 1 December 2021)","Rodriguez-Echeverry, J. & Leiton, M. (2021) Perdida y fragmentacion de ecosistemas boscosos nativos y su influencia en la diversidad de habitats en el hotspot Andes tropicales. Revista Mexicana de Biodiversidad 92: e 923449. https: // doi. org / 10.22201 / ib. 20078706 e. 2021.92.3449"]}

Linum longipes Rose (1906: 117). (Fig. 7a). Type:— MEXICO. Guerrero: In mountains near Iguala, Pringle 9261 (holotype US!, isotypes GH!, MICH!, MSC). Description: — Herbs, annual, thin, 22–34 cm in height; glabrous, except for a few short hairs near the nodes and the base of branches; root thin; stems erect, simple, unbranched to the middle part, essentially glabrous. Leaves entire; basal leaves arranged in whorls of 4, obovate; distal leaves alternate, ovate; (5.3)14.0–18.0 × (2.5)7.5–9.0 mm, petioles 0.1–1.0(2.0) mm long, apex obtuse; 1-nerved, prominent on the abaxial surface; slightly rough, glabrous; stipular glands present at the base, but not well developed. Inflorescence a widely open cymose panicle occupying half or more of the plant height, pedicels 7.0–17.0 mm long; bracts 2.0- 2.8 mm long, margin entire, apex acute-acuminate, stipular glands absent; sepals persistent, ovate, 2.0–2.5(2.7) × 0.8–1.2 mm, margin entire or with minute glands, apex acuminate, 3-nerved, stipular glands absent; petals yellow, obovate, 4.0 mm long, glabrous; stamens 3.0–4.0 mm long; anthers 0.4 mm long, light yellow; staminodia present; styles fused to near the apex, 1.7–2.3 mm long; stigmata capitate, yellow. Fruit widely ovoid, light yellow, 1.8–1.9 × 1.2–1.9 mm, glabrous, pericarp thin, apex apiculate, dehiscent into 10 segments, false septa incomplete with some marginal hairs; seeds elliptical, light brown, whitish cover, 0.4-0.6 × 1.0– 1.1 mm. Distribution: —Endemic to Mexico, in Guerrero, Morelos, and Puebla (Fig. 2a). Habitat and ecology: —Oak forests, low deciduous tropical forest. Elevation 700–1600 m. Cambisol, Lithosol, and Rendzina soil types. Phenology:—Flowering and fruiting in October. Note: — Linum longipes shares a similar morphology with L. cruciata; however, when reviewing the herbarium material, longer pedicels, glabrous, and fused styles are observed as unequivocal characters of L. longipes. Besides, the species shows the unique trait of a few minute hairs near all nodes and at the base of branches. Conservation status: — Linum longipes has an EOO of 416.473 km 2 and an AOO of 16 km 2. In addition to being endemic, the species is known from Specimens examined: — MEXICO. Guerrero: Iguala, Mountains near Iguala, 1514 m, 18°22’46.23”N, 99°28’25.71”W, 11 October 1900, C.G. Pringle 9261 (MEXU!). Morelos: Jojutla, Cerro del Higuerón, 750 m, 14 October 1984, I. Rivera 25 (MEXU!, UAMIZ!). Puebla: Izúcar de Matamoros, 2 October 1942, F. Miranda 2222 (MEXU!); Izúcar de Matamoros, Tropical Deciduous Forest at Puerto Las Palmas, 1525 m, 12 October 1986, D.E. Breedlove & F. Almeda 65221 (MEXU!); Izúcar de Matamoros, Carretera Izúcar-Huajuapan de León, 1300 m, 18°31’33”N, 98°25’05”W, 30 October 1994, J.L. Panero et al. 5302 (MEXU!)., Published as part of González-Velasco, Juan, Burgos-Hernández, Mireya, Galván-Escobedo, Iris G. & Castillo-Campos, Gonzalo, 2022, Taxonomic update of the flax family in Mexico, pp. 141-184 in Phytotaxa 549 (2) on pages 156-157, DOI: 10.11646/phytotaxa.549.2.3, http://zenodo.org/record/6622753, {"references":["Rose, J. N. (1906) Linum longipes. Linum nelsonii. Contributions from the United States National Herbarium 10: 117.","IUCN (2019) Guidelines for Using the IUCN Red List Categories and Criteria. Version 14. Prepared by the Standards and Petitions Subcommittee. Downloadable from: https: // www. iucnredlist. org / resources / redlistguidelines (accessed 22 April 2022)"]}

Linum flagellare H.P.J. Winkler (1931: 116). (Fig. 6b). Type:— MEXICO. Coahuila: Parras, Purpus 1122 (holotype NY!, isotypes F, GH!, MO!, UC). Cathartolinum flagellare Small (1907g: 78). Linum coahuilense C.M. Rogers (1964b: 279). Type:— MEXICO. Coahuila. 10 mi W of Saltillo, Correll & Johnston 21403 (LL!). Description: — Herbs, perennial, 25–40 cm in height, glabrous, glaucous, root thick; stems erect, more or less branched throughout, glabrous. Leaves entire, alternate, basal leaves sometimes opposite, linear to linear-lanceolate, (5.0)11.0– 17.0 × (0.5) 0.7–1.7 mm, sessile, apex slightly acuminate, 1-nerved, coriaceous, glabrous; stipular glands generally absent, sometimes present only in basal leaves. Inflorescence a cymose panicle, more or less diffuse, branches thin, pedicels 2.1–8.3 mm long; bracts 2.2–2.7 mm long, margin entire, apex acuminate; sepals persistent, narrowly lanceolate, 2.0–5.6 × 0.9–1.3 mm; margin scariose, with sparse glandular teeth, apex extremely acute; 1-nerved, stipular glands absent; petals yellow, brownish-red when dried, closely narrow or oblanceolate, 4.0–8.0 mm long, glabrous; stamens 2.0–4.0 mm long; anthers 0.6-1.0 mm long, yellow; staminodia minute, sometimes absent; styles connate at the base to fused to half their length, 1.4–2.4 mm long; stigmata capitate, yellow. Fruit widely ovoid, yellow, 2.4–3.3 × 2.3–2.6 mm, glabrous, pericarp thin, apex pointed, dehiscent into 10 segments, false septa partially developed, septa sparsely ciliate but conspicuous along the margin; seeds elliptical, light brown, 1.6–2.0 × 1.0– 1.2 mm. Distribution: —Endemic to Mexico, in Coahuila, Nuevo Leon, and Zacatecas (Fig. 2b). Habitat and ecology: —Cardonal shrublands, crassi-rosette-leaved thorny shrublands, oak forests, oak-pine forests, yucca shrublands, thornless or sub-thornless small-leaved shrubland, high or medium sub-evergreen tropical forests, low deciduous thorny tropical forest, sandy arid desert vegetation. Elevation 1400–2250 m. Phaeozem, Lithosol, Regosol, and Xerosol soil types. Phenology: —Flowering in March–September; fruiting in March–October. Note: — Linum flagellare is quite variable in terms of habit, flower size, presence of stipular glands, and style attachment. It is usually confused with L. rupestre, which is far more common and with which it shares a similar habit, but from which it can be differentiated by the absence of stipular glands in most leaves, much smaller styles connate at the base or attached to half or almost half its length. In addition, petals exhibit a brownish-red color when dried, a character that persists and is observed in herbarium specimens. Conservation status: —According to the IUCN (2019) B criterion, L. flagellare is VU (B2abc(iii)), with an EOO of 28,947.347 km 2 and AOO of 36 km 2. It is worth mentioning that according to an evaluation carried out by CONABIO (2021), its habitat is constantly threatened by anthropic activities. Specimens examined: — MEXICO. Coahuila: Parras, Sierra de Parras, 2000 m, 25°21’00”N, 102°12’00”W, 19 September 1993, G. Nesom et al. 7645 (MEXU!); Saltillo, Suroeste de la Sierra de Zapalinamé, 2013 m, 25°14’32”N, 101°04’13”W, 15 April 2015, J.A. Encina & J.M. Cárdenas V. 4429 (ANSM!); Saltillo, Slope near Las Barrancas, 3 May 1959, D.S. Correll & I.M. Johnston 21403 (CHAPA!, MEXU!); Saltillo, Sierra de Zapalinamé, 2245 m, 25°15’26”N, 101°03’19”W, 16 August 2014, J.A. Encina et al. 3903 (CIIDIR!); 1.5 miles SW of Las Delicias, 1615 m, 26°14’00”N, 102°49’00”W, 15 August 1973, J. Henrickson 12476 (MEXU!); 3 km al S de El Frayle, 1953 m, 25°00’47”N, 101°20’06”W, 1 October 2016, M.A. Ayala-Ramos et al. 60 (MEXU!); 30 km WSW of Villa Ocampo, 1600 m, 27°15’00”N, 102°41’00”W, 26 September 1986, J. Henrickson & L. Woodruff 20376 (MEXU!). Nuevo Leon: Bustamante, Bustamante Canyon, 496 m, 26°32’58.45”N, 100°33’18.68”W, 13 August 1988, T.F. Patterson 6591 (TEX!). Zacatecas: Concepción del Oro, km 199 de la carretera Zacatecas-Saltillo, 1850 m, 7 May 1977, J. García P. 316 (CHAPA!); 2.5 miles NNE of Estación Camacho, 1860 m, 24°47’00”N, 102°13’00”W, 25 September 1973, J. Henrickson 13520 (MEXU!); 5 km by road WSW of Caopas, 1940 m, 24°46’00”N, 102°12’40”W, 28 March 1973, M.C. Johnston et al. 10453 (MEXU!); 7.5 km by road WSW of Caopas on road to Camacho, 1890 m, 24°45’20”N, 102°13’30”W, 28 March 1973, M.C. Johnston et al. 10449 (MEXU!)., Published as part of González-Velasco, Juan, Burgos-Hernández, Mireya, Galván-Escobedo, Iris G. & Castillo-Campos, Gonzalo, 2022, Taxonomic update of the flax family in Mexico, pp. 141-184 in Phytotaxa 549 (2) on page 154, DOI: 10.11646/phytotaxa.549.2.3, http://zenodo.org/record/6622753, {"references":["Small, J. K. (1907 g) Cathartolinum flagellare. North American Flora 25: 78.","Rogers, C. M. (1964 b) Linum coahuilense. Rhodora 66: 279.","IUCN (2019) Guidelines for Using the IUCN Red List Categories and Criteria. Version 14. Prepared by the Standards and Petitions Subcommittee. Downloadable from: https: // www. iucnredlist. org / resources / redlistguidelines (accessed 22 April 2022)","CONABIO (2021) Indice de Impacto Humano en la Biodiversidad Terrestre. Comision Nacional para uso y conocimiento de la Biodiversidad. Available from: http: // geoportal. conabio. gob. mx / metadatos / doc / html / indihum 14 gw. html (accessed 1 December 2021)"]}