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The aim of this work was to describe the epidemiological, clinical and pathological aspects of two outbreaks of spontaneous poisoning caused by Froelichia humboldtiana in cattle in Pernambuco, northeastern Brazil and reproduce experimentally this poisoning in cattle. Spontaneous poisonings of primary photosensitization occurred in two farms at the municipalities of Cachoeirinha and São Caetano and affected twenty-two adult bovines and two suckling calves after the rainy season. All bovines have recovered 21 days after they were removed from the pasture. To reproduce experimental poisoning, three cows and a calf were maintained in a pasture with 1ha composed by F. humboldtiana during 14 days. Clinical signs and skin lesions were similar in both spontaneous and experimental poisoning and consisted of cutaneous itching and hyperemia of non-pigmented areas of skin that evolved into edema, exudative dermatitis and extensive areas of skin necrosis. Serum levels of aspartate aminotransferase (AST), gamma glutamyltransferase (GGT), total, direct and indirect bilirubin were normal in all cattle examined. Histologically, lesions consisted of epidermal necrosis, hyperkeratosis with large amounts of degenerate neutrophils and acanthosis. In the dermis, edema and inflammatory infiltrate composed of eosinophils, lymphocytes and plasma cells mainly around the blood vessels were observed. In the experimental group, clinical signs of photosensitization were observed after the third day of F. humboldtiana consumption. The suckling calf displayed mild clinical signs of photodermatitis on the 8th day of the experiment. It was estimated that the average consumption of F. humboldtiana necessary to initiate clinical signs in each adult bovine was 78kg.

Amaranthaceae is a cosmopolitan and diverse family, with characteristics that enable plants to occupy habitats with harsh environmental conditions. The Brazilian Cerrado has numerous features that impose challenges to plant survival, such as seasonal drought and fires. Nearly one hundred species of Amaranthaceae occur in the Cerrado and many of them have thickened belowground systems that store non-structural carbohydrates. In this study, we analyze patterns in the adaptive strategies of Amaranthaceae species that occur in the Cerrado, by assessing the types of carbohydrates stored in the belowground systems and biomass allocation in light of photosynthetic characteristics reported in the literature. We analyzed species of Amaranthus (C4), Alternanthera (C3-C4), Froelichia (C4), Gomphrena (C4), and Pfaffia (C3). All the analyzed species had non-structural carbohydrate content higher than 20% of the dry mass. Sucrose was the main non-structural carbohydrate found in the belowground organs of Alternanthera tenella and Amaranthus viridis. Starch was detected only in Amaranthus viridis. All other species accumulate fructans; Pfaffia spp. have inulin-type fructans while Gomphrena and Froelichia have levan-type fructans. Two morphophysiological syndromes are characterized by the lowest or highest investment in belowground system mass and storage of fructans, being interpreted as generalist or specialist adaptive strategies. These two characteristics of such syndromes, together with the photosynthetic metabolisms are traits that reflect the diversity of the Amaranthaceae and their ability to occupy several habitats, including those marked by harsh conditions, such as the Cerrado.

Se designan lectotipos para 36 nombres específicos y 22 nombres infraespecíficos correspondientes a la familia Amaranthaceae de la Flora Argentina, los que pertenecen a los géneros actualmente aceptados Alternanthera, Blutaparon, Chamissoa, Froelichia, Hebanthe y Pfaffia. Del total, 20 corresponden a lectotipificaciones de segundo paso. Lectotypifications in Amaranthaceae for Flora Argentina. Lectotypes are designated for 36 species and 22 infraspecific taxa of Amaranthaceae for Flora Argentina which belong to the currently accepted genera Alternanthera, Blutaparon, Chamissoa, Froelichia, Hebanthe, and Pfaffia. Of all the lectotypifications, 20 are second step lectotypifications.

Froelichia lanata f. roseiflora Chodat in Bull. Herb. Boissier ser. 2, 3: 354. 1903 [nom. nud.]. = Froelichia procera (Seub.) Pedersen [Pedersen, 1967: 448]., Published as part of Ramella, Lorenzo, 2016, Nomenclatura, tipificaciones y sin��nimos nuevos en la familia Amaranthaceae de la Flora del Paraguay, pp. 311-326 in Candollea 71 (2) on page 322, DOI: 10.15553/c2016v712a16, http://zenodo.org/record/5721803, {"references":["Pedersen, T. M. (1967). Studies in south american Amaranthaceae. Darwiniana 14: 430 - 462."]}

Froelichia procera (Seub.) Pedersen in Darwiniana 14: 448. 1967. �� Froelichia lanata var. procera Seub. in Mart., Fl. Bras. 5(1): 167. 1875. = Froelichia lanata var. laciniata Suess. in Repert. Spec. Nov. Regni Veg. 39: 6. 1935, syn. nov. Holotypus: PARAGUAY. Guair��: ���Ea. Primera ���, I.1932, J��rgensen, P. 4717 (MO [MO- 256764] [foto]!). Isotypi: (BR, C, S). F. lanata var. laciniata: Pedersen (1967: 449) incluye entre los espec��menes determinados como F. procera a la colecci��n J��rgensen 4717 sin darse cuenta que se trata del tipo de la var. laciniata . Formalizamos aqu�� la opini��n taxon��mica de Pedersen, con la publicaci��n de este sin��nimo nuevo., Published as part of Ramella, Lorenzo, 2016, Nomenclatura, tipificaciones y sin��nimos nuevos en la familia Amaranthaceae de la Flora del Paraguay, pp. 311-326 in Candollea 71 (2) on page 316, DOI: 10.15553/c2016v712a16, http://zenodo.org/record/5721803, {"references":["Pedersen, T. M. (1967). Studies in south american Amaranthaceae. Darwiniana 14: 430 - 462."]}

Froelichia lanata f. albiflora Chodat in Bull. Herb. Boissier ser. 2, 3: 354. 1903 [nom. nud.]. = Froelichia procera (Seub.) Pedersen [Pedersen, 1967: 448]., Published as part of Ramella, Lorenzo, 2016, Nomenclatura, tipificaciones y sin��nimos nuevos en la familia Amaranthaceae de la Flora del Paraguay, pp. 311-326 in Candollea 71 (2) on page 322, DOI: 10.15553/c2016v712a16, http://zenodo.org/record/5721803, {"references":["Pedersen, T. M. (1967). Studies in south american Amaranthaceae. Darwiniana 14: 430 - 462."]}

Three outbreaks of primary photosensitization caused by Froelichia humboldtiana are reported in the semiarid region of the states of Pernambuco and Paraíba, in northeastern Brazil. The disease occurred from March to June 2011, affecting 27 bovines out of a total of 70. The main lesions consisted of dermatitis of the white skin, with edema and necrosis. All the bovines recovered after removal from the areas invaded by F. humboldtiana. To produce the disease experimentally, one bovine with white skin was placed for 14 days into an area with F. humboldtiana as the sole forage. This bovine presented photodermatitis on the third day of consumption. The serum concentrations of total, indirect, and conjugated bilirubin and the serum activities of gamma-glutamyl transferase (GGT) and aspartate-aminotransferase (AST) in the spontaneously affected cattle and in the experimental cattle remained within normal ranges. It is concluded that F. humboldtiana causes primary photosensitization in cattle in northeastern Brazil.

Fotossensibilização é freqüente em eqüinos no semi-árido da região Nordeste, mas jumentos, mulas, ovinos e bovinos são, também, afetados. A dermatite afeta, principalmente, áreas de pele despigmentadas e os animais se recuperam após serem retirados das pastagens. Para comprovar a etiologia da enfermidade Froelichia humboldtiana (Roem. et Schult.) Seub., coletada no campo foi administrada no mesmo dia da colheita ou após ser mantida em refrigerador por 1-4 dias, por períodos de 30 ou mais dias, ad libitum como único alimento, a 2 jumentos e um ovino branco e, como único alimento volumoso, a um eqüino branco. Esses animais não manifestaram sinais clínicos e as atividades séricas de gama-glutamiltransferase (GGT), aspartato-aminotransferase (AST) e alanino-aminotransferase (ALT) ficaram dentro dos valores normais. Em outro experimento, um ovino foi colocado a pastar diariamente, durante o dia, preso por uma corda em uma área que tinha exclusivamente F. humboldtiana, por um período de 26 dias. Lesões características de fotossensibilização foram observadas 4-5 dias após o início do experimento. Após cessar o consumo da planta, no 26º dia, o ovino recuperou-se totalmente em 30 dias. Em outro experimento, 4 ovinos foram também colocados, presos por cordas, na mesma área. Outros 4 permaneceram como controles em uma pastagem vizinha, mas sem F. humboldtiana. Lesões de pele, características de fotossensibilização foram observadas após 11-25 dias de consumo de F. humboldtiana. As atividades séricas de AST e GGT, e os níveis de bilirrubina sérica permaneceram dentro dos valores normais. No final do período de permanência em pastagens de F. humboldtiana, 2 ovinos foram abatidos e 2 foram retirados da pastagem. Os que foram abatidos não apresentaram lesões macroscópicas nem histológicas do fígado; os outros dois se recuperaram das lesões da pele 17 e 20 dias após o fim do pastejo. Uma égua e seu potro foram colocados na mesma pastagem com F. humboldtiana por um período de 44 dias. A égua, que não tinha áreas de pele despigmentadas não apresentou lesões, no entanto o potro desenvolveu dermatite nas áreas brancas de pele 25 dias após o início do pastejo. Após serem retirados da pastagem o potro recuperou-se totalmente em 15 dias. Estes experimentos indicam que F. humboldtiana causa fotossensibilização primária em animais domésticos. A ausência de lesões nos animais que ingeriram a planta após ser coletada e mantida em geladeira sugere que a planta perde sua toxicidade depois da coleta. A ausência de lesões oculares características da intoxicação por furocumarinas sugere que F. humboldtiana contém derivados da naftodiantrona, similares aos encontrados em Fagopyrum esculentum e Hypericum perforatum que não causam lesões oculares. Photosensitization is common in the Brazilian semiarid, affecting mainly horses, but also donkeys, mules, sheep and cattle. The dermatitis affects mainly non pigmented skin, and the animals recover after being withdrawn from the pastures. To demonstrate the etiology of the disease, Froelichia humboldtiana (Roem. et Schult.) Seub., collected in the field one or two times a week and kept in the refrigerator for 1-4 days, was administered for 30 or more days as the only food ad libitum to 2 donkeys and one white sheep, and as the only forage ad libitum, to one white horse. No clinical signs were observed in those animals, and serum activities of aspartate-aminotransferase (AST), alanine-aminotransferase (AST), and gamma-glutamyltransferase (GGT) were within normal ranges. In another experiment, one sheep was tied by a rope, during the day, in a pasture of exclusively F. humboldtiana for a 26 days period. Skin lesions characteristic of photosensitization appeared 4-5 days after the start of the experiment and became severe until day 26. After the withdrawal of the animal from the pasture on day 26 it fully recovered within 30 days. In another experiment, 4 sheep were tied by ropes in the same pasture, during the day, for a 29 days period. Another 4 control sheep were maintained in a neighboring pasture without F. humboldtiana. Skin lesions characteristic of photosensitization were observed after 11-25 days of F. humboldtiana grazing. Serum activities of AST and GGT, and serum levels of bilirubin were within normal ranges. At the end of the 29 days grazing F. humboldtiana, 2 sheep were euthanized, and 2 were withdrawn from the pastures. No gross or histologic liver lesions were observed on the 2 sheep euthanized; the other 2 sheep recovered within 17 and 20 days after the end of grazing. One mare and its foal grazed in the same pasture during 44 days. The mare that had a pigmented skin had no dermatitis, but the foal showed dermatitis on the white areas of the skin after 25 days of grazing. The two horses were withdrawn from the pastures after 44 days grazing, and the foal fully recovered within 15 days. These experiments indicate that F. humboldtiana causes primary photosensitization in domestic animals. The absence of lesions in animals ingesting the plant collected in the field and kept refrigerated suggests that F. humboldtiana lost toxicity after collection. The absence of lesions in the eyes of affected animal, which are characteristic of primary photosensitization caused by furocoumarins containing plants, suggests that F. humboldtiana contains a naphthodianthrone derivate, similar to those found in Fagopyrum esculentum and Hypericum perforatum which do not cause eye lesions.

The North American genus Tidestromia (Amaranthaceae: Gomphrenoideae), with high levels of endemism in the Chihuahuan Desert, is subjected to phylogenetic analysis using 19 morphological characters. Species from genera most closely related to Tidestromia (Alternanthera, Froelichia, Gossypianthus, and Guilleminea), as well as the more distantly related genus Iresine, were used as outgroups. The monophyly of Tidestromia is well supported by four synapomorphies: alternate leaves, dichasial inflorescences, and pollen that is psilate (homoplasious) and with mesoporia that are narrowed distally. The single most parsimonious tree resolved T. valdesiana as sister to the rest of Tidestromia, which is apomorphically diagnosed by the presence of involucres. The annual habit supports a clade comprising T. carnosa, T. lanuginosa, and T. tenella, which is nested among the species with involucres. The phylogenetic relationships of the rest of the taxa remain unresolved. Traditional morphological evidence thus is important for circumscribing the genus Tidestromia, but shows limited utility for resolving species groups within this genus.

Two new species, one new variety, and a new combination of Froelichia are described from North America. Froelichia xantusii from Baja California Sur is being recognized as a species endemic to southern Baja California and separate from F. interrupta in which it had been previously included. Within F. interrupta two varieties are here recognized, the newly described Froelichia interrupta var. colimensis from southern Nayarit to Oaxaca and the new combination Froelichia in- terrupta var. alata from the Sonoran Desert. Froelichia latifolia is described from eastern Texas and has been segregated from the widespread F. floridana. A key to the genus in North America is also included. The genus Froelichia Moench is a group of 16 spe- cies, two varieties, and five subspecies native to the Western Hemisphere. It is classified in the subfamily Gomphrenoideae of the Amaranthaceae, a likely monophyletic group consisting of 20 genera centered in the tropical and subtropical regions of North and South America and characterized by having bispo- rangiate anthers and pollen with a reticulate exine and deeply recessed pores (Schinz 1893; Townsend 1993; Borsch 1998). The genus Froelichia consists mostly of herbaceous annuals and perennials, with two shrubby species and associated subspecies occurring in the Ga- lapagos Islands. While the genus is widespread, ex- tending from the southern extreme of Canada to north- ern Argentina and Uruguay, it is most abundant and species-rich in the desert and semi-desert range lands of the southwestern and south-central United States and Mexico and the scrublands of central South Amer- ica in Brazil, Paraguay, and northern Argentina. In all these regions, Froelichia is most common on sandy sub- strates where it can sometimes be the dominant ele- ment in the vegetation, though more commonly it is a minor component of the flora. Froelichias are recognized mostly by their spikes of small, densely wooly flowers, a characteristic that has inspired its common names Cottonweed and Snake- cotton. At a more technical level, Froelichia is distin- guished by the unique feature among the Amarantha- ceae of a fully indurate perianth that surrounds and is dispersed with the fruit. This perianth (often implicitly included as part of the ''fruit'' in many flora treat- ments) is characteristically winged on its lateral mar- gins, though the size and dissection of these wings will vary among species and to a lesser extent among in- dividuals. During the course of a full taxonomic revision of Froelichia in North America (McCauley 2002) it became evident that the current circumscription of the species did not adequately represent the diversity of taxa across the study area. Multivariate morphological and molecular phylogenetic analyses in conjunction with extensive field observations indicated a series of dis- crete entities deemed significantly unique morpholog- ically and phylogenetically from more widespread taxa and restricted to limited geographical ranges to warrant taxonomic recognition. Thus, two new species and two varieties are here being recognized. The two new species are being segregated from common wide-ranging taxa that have been recognized as possessing high levels of morphological variability, F. latifolia R.A. McCauley from F. floridana (Nutt.) Moq. and F. xantusii R.A. McCauley from F. interrupta (L.) Moq. Two varieties, both of F. interrupta, represent dis- crete morphological forms that are geographically seg- regated though phylogenetically they show little dif- ferentiation from the typical form of the species.

Froelichia floridana (cottonweed) occurs as a disjunct population along the Ohio River in southeastern Ohio. The anomalous occurrence of F. floridana in this area has led to its designation as a state endangered species and a management regime to maintain the habitat conditions in which it occurs. As part of this effort, a restoration site was established on public lands in 1984 from seed collected in areas threatened by development. This study seeks to determine the demographic characteristics of this species in the restored and non-restored managed sites to provide basic ecological information regarding life history parameters and to judge the effectiveness of the restoration. For two years (1997–1998) we collected information on seed bank abundance, field seed germination, plant survivorship, and seed production to create a stage-based transition matrix model. The model suggests that population growth and abundance as assayed by λ (rate of increase) are stable to declining and are similar between the restoration and natural sites. A reduction in competition had a positive effect on population growth. Elasticity analysis showed that plants germinating earlier in the spring and becoming established as an early cohort contributed a greater level of reproductive output than plants germinating in late spring. Lowered population growth for 1997 is attributed to a cooler and dryer than average early spring that delayed germination and subsequent seed production. Elasticity analysis also suggested that the presence of a persistent seed bank was crucial for long-term population maintenance and may allow for recovery in areas of low aboveground abundance through soil manipulation.

Froelichia (Amaranthaceae) is reported from the Sahel of Senegal for the first time. This is a new generic record for Africa and is a cause for concern since the genus is known to be an invasive weed in other countries with warm climates and sandy substrates. The difficulties caused by this taxon are summarised and control measures are suggested.

Aerial parts of 23 species distributed in 10 genera of the Amaranthaceae have been examined for the presence of betaines. Glycinebetaine was isolated from all the species studied and, in addition, trigonelline was detected in eight out of the nine species of Amaranthus , 1 of the two species of Alternanthera and in the species of Iresine (3), Celosia (2), Chamissoa (1), Aerva (1), Gomphrena (1) and Froelichia (1). With the exception of I. herbstii , glycinebetaine was the predominant betaine. The highest yield of this compound was from Cyathula geniculata (2.11%, dry weight), but, with the exception of I. herbstii (0.05%), the species tested had contents in the range 0.28–2.11%, dry weight. Trigonelline yields varied from 0.004 to 0.15%, dry weight. From the data obtained, classification of the Amaranthaceae as a betaine – accumulating family would appear to be justified.

A new phytoecdysteroid, 2-dehydro-3- epi -20-hydroxyecdysone, together with 20-hydroxyecdysone have been isolated by bioassay/RIA-directed HPLC analyses of a methanol extract of the seeds of Froelichia floridana . The structure of the novel ecdysteroid was determined unambiguously by UV, LSIMS, and a combination of 1D and 2D NMR techniques. The biological activity in the Drosophila melanogaster B II cell bioassay (ED 50 =4.0×10 −7 M) is considerably lower than that of 20-hydroxyecdysone (ED 50 =7.5×10 −9 M).

Phylogenetic relationships within the angiosperm order Caryophyllales were investigated by comparative sequencing of two portions of the highly conserved inverted repeat (totaling some 1100 base pairs) coinciding with the region occupied by ORF2280 in Nicotiana, the largest gene in the plastid genomes of most land plants. Data were obtained for 33 species in 11 families within the order and for one species each of Plumbaginaceae, Polygonaceae, and Nepenthaceae. These data, when analyzed along with previously published ORF (open reading frame) sequences from Nicotiana. Spinacia. Epifagus, and Pelargonium using parsimony, neighbor-joining, and maximum likelihood methods, reveal that: (1) Amaranthus, Celosia, and Froelichia (all Amaranthaceae) do not comprise a monophyletic group; (2) Amaranthus may be nested within a paraphyletic Chenopodiaceae; (3) Sarcobatus (Chenopodiaceae) is allied with Nyctaginaceae + Phytolaccaceae (the latter family excluding Stegnosperma but including Petiveria); and (4) Caryophyllaceae (with Corrigiola basal within the clade) are sister group to Chenopodiaceae + Amaranthaceae. Basal relations within the order remain obscure. Sequence divergence values in pairwise comparisons across all Caryophyllales taxa ranged from 0.1 to 5% of nucleotides. However, despite these low values, 23 insertion and deletion events were apparent, of which five were informative phylogenetically and bolstered several of the relationships listed above. A polymerase chain reaction (PCR) survey for ORF homolog length variants in representatives from 70 additional angiosperm families revealed major deletions, of 100 to 1400 base pairs, in 19 of these families. Although the ORF is located within the mutationally retarded inverted repeat region of most angiosperm chloroplast DNAs, this gene appears particularly prone to length mutation.

C(4) photosynthesis evolved multiple times in the Amaranthaceae s.s., but the C(4) evolutionary lineages are unclear because the photosynthetic pathway is unknown for most species of the family. To clarify the distribution of C(4) photosynthesis in the Amaranthaceae, we determined carbon isotope ratios of 607 species and mapped these onto a phylogeny determined from matK/trnK sequences. Approximately 28% of the Amaranthaceae species use the C(4) pathway. C(4) species occur in 10 genera-Aerva, Amaranthus, Blutaparon, Alternanthera, Froelichia, Lithophila, Guilleminea, Gomphrena, Gossypianthus, and Tidestromia. Aerva, Alternanthera, and Gomphrena contain both C(3) and C(4) species. In Aerva, 25% of the sampled species are C(4). In Alternanthera, 19.5% are C(4), while 89% of the Gomphrena species are C(4). Integration of isotope and matK/trnK data indicated C(4) photosynthesis evolved five times in the Amaranthaceae, specifically in Aerva, Alternanthera, Amaranthus, Tidestromia, and a lineage containing Froelichia, Blutaparon, Guilleminea, Gomphrena pro parte, and Lithophila. Aerva and Gomphrena are both polyphyletic with C(3) and C(4) species belonging to distinct clades. Alternanthera appears to be monophyletic with C(4) photosynthesis originating in a terminal sublineage of procumbent herbs. Alpine C(4) species were also identified in Alternanthera, Amaranthus, and Gomphrena, including one species (Gomphrena meyeniana) from 4600 m a.s.l.

Gomphrena interrupta Linnaeus, Species Plantarum 1: 224. 1753. "Habitat in America." RCN: 1842. Lectotype (Veldkamp in Taxon 30: 209. 1981): Houstoun, Herb. A. van Royen No. 908.260-241 (L; iso- BM). Current name: Froelichia lanata (L.) Moq. (Amaranthaceae). Note: Mears (in Taxon 29: 87. 1980) stated that the Royen specimen had been recently lost and designated Houstoun s.n. (BM!) as neotype. Veldkamp (in Taxon 30: 209. 1981) reported that this was incorrect and rejected Mears��� choice in favour of van Royen���s sheet (original material for the name)., Published as part of Jarvis, Charlie, 2007, Chapter 7: Linnaean Plant Names and their Types (part G), pp. 529-556 in Order out of Chaos. Linnaean Plant Types and their Types, London :Linnaean Society of London in association with the Natural History Museum on page 529, DOI: 10.5281/zenodo.291971

Phenetic analyses of morphological variation were used to elucidate distinctiveness and circumscription of taxa within, the genus Froelichia in North America. Preserved specimens representing all recognized taxa and one suspected hybrid taxon were measured for 39 continuous and discrete characters and subjected to univariate and multivariate analyses. Principal coordinate analysis indicated the presence of three distinct groups of species with intergradation of morphological intermediates. Two of the groups corresponded to two large complexes of species, the F. floridana complex of the south-central and southeastern United States and the F. interrupta complex, principally of Mexico, while the third consisted of F. gracilis native to the southern United States and adjoining Mexico. Discriminant analysis on each of the two complexes indicated morphologically distinct forms within each morphologically variable complex. The use of novel characters for the discrimination of taxa resulted in the identification of less plastic traits among the recognized species. Use of these newly discovered traits provides more reliable means for the identification of taxa. An instance of potential, hybridization among three taxa in southern Texas was additionally explored with the putative hybrid taxa exhibiting an intermediate combination of morphological traits between each of the putative parents.

Molecular phylogenetic analyses of the nuclear ribosomal DNA internal transcribed spacer (ITS 1 and ITS 2) and the 5.8S gene were used to infer a phylogeny among the ten recognized taxa of Froelichia in North America. Analyses using both maximum parsimony (MP) and maximum-likelihood (ML) depicted a low level of sequence divergence though it was sufficient in most cases to differentiate taxa. Froelichia xantusii, a species restricted to southern Baja California was shown to be the basalmost member of the group subtending three clades. Two of the clades received good bootstrap support in the MP analysis and corresponded to a genetically homogeneous F. interrupta, and a clade comprising the two species F. latifolia and F. texana. A third clade receiving low bootstrap support contained F. floridana, F. gracilis, F. arizonica, and F. drummondii. Species diversity within the genus was centered within the Tamaulipan Brushland region of north-east Mexico and the southern portion of the US state of Texas where taxa from two of the three principal clades occurred, indicating a region of high speciation and diversification within the genus.

The eleven species described as Gomphrena L. by Linnaeus are identified as species of Gomphrena, Alternanthera Forsskail, Caraxeron Rafinesque (= Philoxerus auct. mult., non R. Brown) and Froelichia Moench. Alternanthera flava (L.) Mears, comb. nov., is presented. It is demonstrated that Linnaeus' attitudes about the genus Gomphrena were more closely related to inflorescence characteristics than to stamen and stigma number.

Twenty-three genera of Amaranthaceae occur in the New World. Two endemic genera occur in the Hawaiian Islands. Among the genera of the subfamily Amaranthoideae, Celosia, Cyathula and Achyranthes have their main distributions in the Old World; the two last-named genera are represented in the Americas only by widespread weeds. All the New World genera of the subfamily Gomphrenoideae are mainly or entirely restricted to this region. Characters of androecium and gynoecium are fundamental in the recognition of genera within the family. Androecia of different genera may be structurally and phylogenetically more similar than would appear from a cursory examination. It is suggested that the type of staminal tubes found in Pseudogomphrena and Froelichia can be derived from that in Alternanthera and Froelichiella by reduction of filament length and a fusion of pseudostaminodia with the filaments. The staminal tube in Gomphrena could result from a further decrease in distance between pseudostaminodia of the Pseudogomphrena type, and a deeper forking of the pseudostaminodia; each so-called apical filament lobe in Gomphrena would then be homologous with half a pseudostaminodium in Pseudogomphrena. Much of the variation in the androecia of these and other genera, as well as within genera such as Pfaffia, can be explained as the combined results of coalescence and splitting-up tendencies. Splitting up of staminal tubes may not necessarily take place along the borders of phylogenetically original filaments and pseudostaminodia. The Amaranthus-type of pollen is found in the majority of genera of the subfamily Amaranthoideae, but also in the Chenopodiaceae. A group of genera within the subfamily Gomphrenoideae also has pollen very similar to, or identical with, this type. Most genera of the subfamily Gomphrenoideae have pollen of the Gomphrena-type. Pseudoplantago has unilocular (at anthesis) anthers, a characteristic of the subfamily Gomphrenoideae, but floral structure as well as pollen morphology connect the genus to a group of genera within the Amaranthoideae, subtribe Achyranthinae. The combination of subcuboidal shape and opercula with radially arranged hooked protuberances, makes the pollen of Pseudoplantago unique among the angiosperms studied so far. Floral morphology and palynological characteristics indicate a close relationship between Pfaffia and Alternanthera. Both genera, as currently accepted, are relatively homogeneous from pollen morphological points of view. There are no correlations between pollen morphology and the variation in the androecium in Pfaffia, nor would pollen structure support recognition of Hebanthe as a distinct genus. Woehleria and Irenella may be derived from, or be of the same origin as, Dicraurus and Iresine. All four genera are placed in the subfamily Gomphrenoideae because of the bisporangiate anthers, but their pollen structure is very close to, or identical with, that of the Amaranthus-type. Pseudogomphrena combines characteristics of Gomphrena and Pfaffia.

A B S T R A C T A model which visualizes a species as a set of biotype subsets is useful when considering the degree of fitness and homogeneity of populations in their environment. Under founder principle concepts we expect that the number of such subsets tends to decrease as local populations encounter new selective forces in environments and habitats other than those occupied by predecessor populations. Relations between biotypes,- considered from the point of view of "variation associated with character correlation" or correlated response and polygene systems, imply that the magnitude of product-moment correlations between characters can be used as a general measure of selective stress impinging upon populations. Magnitude is defined as the per cent of the total possible pairs of characters whose correlation coefficients are significantly different from zero. The direction of magnitude expected under the founder principle is from low in an umdisturbed or ancestral situation to high in an alien one. This hypothesis is demonstrated in the genus Froelichia (AMARANTHACEAE). A CONSIDERABLE portion of biologic literature is devoted to evolutionary dynamics. The basic conceptual model postulates that populations survive or become extinct, change or remain unchanted, become partitioned or amalgamated, -multiply or decrease, etc., largely because of gene-environment interaction. The model is so encompassing that component phenomena have been diversely studied for over 100 years. A subsidiary model visualizes a species x as