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A new species of Alternanthera from Kerala (SW-India), named Alternanthera indica, is described and illustrated. A detailed description, photographs, and drawings are provided. The new species resembles A. carcasana, A. paronychioides var. robusta, A. pungens, A. sessilis, and A. tenella for sharing habit and sessile synflorescences, but it differs from these species in several characters (i.e. shape and size of leaves, sepal length and hairiness, and appendages on the androecial tube margin and length).

Alternanthera (Amaranthaceae) is a diverse genus largely restricted to the American Tropics that belongs to the alternantheroid clade containing C4 and C3–C4 intermediate species. This research focuses on the study of pollen characters by studying 13 species, representatives of the two major clades and subclades of Alternanthera. General palynological comparisons were conducted with light microscopy (LM), scanning electron microscopy (SEM) and with confocal laser scanning microscopy (CLSM) for exine ultrastructure. Twenty-five characters were measured and described for Alternanthera and among these, 14 pollen characters were used to discriminate pollen groups using cluster analysis and canonical analysis of principal coordinates (CAP). Pollen form and ornamentation, pores number, spines length, number of ektexinous bodies and nanospines on the ektexinous bodies on pore membranes, arrangement of nanopores and spines on structural elements, and metareticula form were taxonomically important and ther...

Two well-defined new species of Iresine from Mexico are described based on character data covering vegetative and floral morphology, pollen, and sequences of plastid matK-trnK, trnL-F and rpl16 as well as nuclear ITS. We provide morphological and molecular descriptions, as well as a discussion on diagnostic characters and taxonomic affinities. Both species are distributed in cloud forests; I. borschii is known only from two collections in Veracruz, whereas I. sousae has been collected several times in Oaxaca and Chiapas. Both species are illustrated from herbarium specimens to facilitate their recognition. New field collections and observations are needed to improve our knowledge on the habitat and conservation status of these new species. Citation: Flores-Olvera H., Zumaya S. & Borsch T. 2016: Two new species of Iresine (Amaranthaceae: Gomphrenoideae) from Mexico supported by morphological and molecular characters. — Willdenowia 46: 165–174. doi: http://dx.doi.org/10.3372/wi.46.46113 Version of...

During the evolution of vascular plants, C4 photosynthesis has developed > 60 times, but most studies concerning the evolution and the ecophysiological advantages of the C4 syndrome have been carried out in grasses. Among eudicots, C4 photosynthesis has developed in lineages that are morphologically more diverse than the relatively homogeneous grasses, and conclusions about C4 evolution based on grasses may or may not apply to eudicots. Little is known about the origin of C4 photosynthesis in Amaranthaceae s.s., one of the most C4 species-rich lineages of eudicots. Among subfamily Gomphrenoideae, C3 and C4 species are found in arid regions, but high Andean species display the C4 pathway. In this study, we aimed to compare the climatic extremes between C3 and C4 species in Gomphrenoideae. In particular, we evaluated the upper and lower extremes of three climatic variables among closely related C3 and C4 lineages, using phylogenetic generalized least squares (PGLS), applied on four topologies: maximum parsimony, Bayesian and maximum likelihood (ML) topologies including species with available DNA sequences and a ML topology that included unsequenced species with available climate data. We tested whether the evolution of C4 photosynthesis correlates with a niche specialization where both the upper and the lower extremes change position or a niche expansion where only a single extreme changes position. PGLS results showed that C4 species of Gomphrenoideae have specialized to dryer regions and expanded into colder ones than their C3 relatives. However, the niche expansion into colder climates only includes areas with low temperatures during winter, not during the growing period. Finally, we found no evidence for a niche change into warmer climates. Therefore, the model for the evolution of C4 photosynthesis in Gomphrenoideae may differ from the one supported in Chenopodioideae and seems to be more similar to that found in grasses, where the C4 pathway appears to have evolved in humid habitats, but facilitated an expansion into arid ones. However, we found no support for the common expectation that C4 species reach warmer climates than their C3 relatives, contrasting with previous results on grasses. Fil: Bena, María Julia. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Botánica Darwinion. Academia Nacional de Ciencias Exactas, Físicas y Naturales. Instituto de Botánica Darwinion; Argentina Fil: Acosta, Juan Manuel. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Botánica Darwinion. Academia Nacional de Ciencias Exactas, Físicas y Naturales. Instituto de Botánica Darwinion; Argentina Fil: Aagesen, Lone. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Botánica Darwinion. Academia Nacional de Ciencias Exactas, Físicas y Naturales. Instituto de Botánica Darwinion; Argentina

Durante la evolución de las plantas vasculares, la fotosíntesis C4 ha surgido más de 60veces. La mayoría de los estudios que analizaron la evolución y las ventajas ecofisiológicas delsindrome C4 se han realizado en gramíneas. Sin embargo, en dicotiledóneas, la fotosíntesis C4ha surgido en linajes morfológicamente más diversos. Así, las conclusiones sobre la evoluciónde la fotosíntesis basadas en la familia Poaceae, no necesariamente pueden ser aplicadas adicotiledóneas. En la familia Amaranthaceae se estima que la vía C4 podría haber surgidocinco veces de manera independiente, con al menos tres orígenes dentro de la subfamilia Gomphrenoideae. De esta manera, la presente tesis se propone comparar la distribuciónclimática entre especies C3 y C4 de la subfamilia Gomphrenoideae en un contexto filogenético. Para ello, se evaluó el rango de cada especie comparando los extremos superior e inferior detres variables macro-climáticas entre especies C3 y C4. Se utilizó el método “Phylogenetic Generalized Least Squares”y se testeó si la evolución de la fotosíntesis C4 se correlacionacon una especialización de nicho donde ambos extremos de las variables climáticas cambiande posición, o si se correlaciona con una expansión de nicho donde sólo uno de los extremosvaría. Los resultados mostraron que las especies C4 alcanzan regiones más secas y frías quesus parientes C3 más cercanos. No obstante, la expansión hacia climas más fríos sólo incluyóáreas con bajas temperaturas durante el invierno. No se encontraron evidencias de un cambiode nicho hacia regiones más cálidas. Durante la compilación de datos realizada en la primer etapa de esta tesis, surgió lanecesidad de clarificar el estado taxonómico de numerosos nombres. Por consiguiente, en unasegunda parte se realizó una detallada b´usqueda bibliográfica y compilación de ejemplarestipo para las especies del género Gomphrena. A partir de la observación de ejemplares deherbario, se identificaron los caracteres diagnósticos y se confeccionó una clave dicotómicapara las especies de Gomphrena del Cono Sur. During the evolution of vascular plants, C4 photosynthesis has arisen more than 60times. Most studies concerning the evolution and the ecophysiological advantages of the C4syndrome have been carried out in grasses. However, among eudicots, C4 photosynthesishas developed in lineages that are morphologically more diverse. Therefore, conclusions concerning C4 evolution based on grasses may not necessarily be applied to eudicots. Withinthe Amaranthaceae family, it is estimated that the C4 pathway could have arisen five timesindependently, with at least three different origins among the subfamily Gomphrenoideae. Hence, this thesis aims to compare the climatic distribution among C3 and C4 species within Gomphrenoideae in a phylogenetic context. With that purpose, the range of each specieswas evaluated, comparing the upper and lower extremes of three macro-climatic variablesbetween C3 and C4 species. The method of “Phylogenetic Generalized Least Squares”wasemployed and it was tested whether the C4 evolution correlates with a niche specializationwhere both macro-climatic extremes change position, or if it correlates with a niche expansionwhere only one extreme changes. The results showed that C4 species reach dryer andcolder regions than their closest C3 relatives. Notwithstanding, expansion into colder climatesonly included areas with low temperatures during winter. No evidences for a niche changeinto warmer climates were found. In the course of data collection conducted during the first stage of this thesis, the need toclarify the taxonomic status of many names arose. Therefore, in the second stage, a detailedliterature search and compilation of type specimens of the Gomphrena species were carriedout. From the observation of harbarium specimens, the diagnostic traits were identified anda dichotomic identification key for Gomphrena species from the Southern Cone was prepared. Fil: Bena, María Julia. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.

Background and aims – Amaranthaceae comprise the former Chenopodiaceae, Beta, and core-Amaranthaceae. Particularly in the Gomphrenoid clade, most species have flowers with an 'androecial tube'. On its rim and alternating with the stamens, so-called (pseudo-)staminodia occur. However, neither their origin nor function have been clarified. We aimed to determine the nature of both the 'androecial tube' and pseudostaminodia in species of three genera: Iresine, Alternanthera and Tidestromia . In addition, we also aimed to document the development of the gynoecium. Methods – Scanning electron microscopic (SEM) and light microscopic (LM) observations of the floral development. Key results – Five individual sepal primordia appear in quincuncial order, followed by the appearance of five individual stamen primordia opposite them. At semi-maturity, the stamens are raised by the formation of a tube below them, with at its inside surface a glandular zone. Alternating with the stamens, appendages develop from individual primordia on the rim of the androecial tube. In bisexual/female flowers, from a primary gynoecium primordium, secondarily, an annular gynoecium wall primordium is formed, surrounding a central zone from which a single ovule develops. At maturity, the gynoecium stands on a gynophore. In Alternanthera microcephala, the gynophore may become large, sometimes developing appendages. Conclusions – Our hypothesis that the androecial tube develops from an underlying annular intercalary meristem is supported by the absence of an annular androecium primordium and the late development of the androecial tube. The 'pseudostaminodes' are appendages of the androecial tube. Their often conspicuous appearance and the glandular inside surface of the androecial tube suggest an animal(insect)-based pollination syndrome. We consider the androecial tube, the staminal ring in flowers of Beta vulgaris and the 'fused filaments' in some Chenopodioideae as morphological homologues. We suggest that the development of the gynoecium wall might be decoupled from the development of the ovule.

Iresine rzedowskii Zumaya, Flores Olv. & Borsch and I. valdesii Zumaya, Flores Olv. & Borsch are described, illustrated, and compared to morphologically similar species. In addition, pollen SEM micrographs and distribution maps are provided for the new species. Iresine rzedowskii is a shrub with long clambering stems, the younger ones reddish with conspicuous lenticels and the older ones with suberose cortex. It is the only species of Iresine that has pollen grains with a foveolate tectum. Iresine valdesii is also a shrub but with stiff erect branching and small, perennial coriaceous leaves. The synflorescences of staminate plants are solitary, very small, usually once-branched thyreoid structures while those of pistillate plants are very different, with paracladia appearing terminal on most branches and erect, up to 13 cm long, and two to three times branched. Both species are restricted to Mexico. Iresine rzedowskii ranges from northwestern Chihuahua to northern Oaxaca, while I. valdesii is end...

Alternanthera (Amaranthaceae) is a diverse genus (80–200 species) largely restricted to the American Tropics. With Pedersenia and Tidestromia, it makes up the ‘Alternantheroid clade’ in Gomphrenoideae. Parsimony and Bayesian analyses of nucleotide sequences of nuclear (ITS) and plastid (rpl16, trnL-F) and morphological characters identify that the capitate stigma of Alternanthera is a synapomorpy within the Alternantheroids. Within Alternanthera, two major clades were resolved, both of which were marked by otherwise homoplasious characters of the gynoecium: Clade A [99% jackknife (JK); 1.0 posterior probability (PP)] with nine species and Clade B (60% JK; 0.98 PP) with 22 species. Four subclades (B1–B4), strongly supported statistically, were identified in Clade B. Previous subgeneric classifications of Alternanthera appear artificial in light of our new molecular phylogenetic analyses. Most major lineages are congruently resolved by nuclear and plastid data but some incongruence between the nrITS and plastid phylogenetic trees suggests hybridization may have played a role in the rampant speciation in Alternanthera. Whereas C4 photosynthesis appears to have evolved in a single clade, the position of A. littoralis var. maritima (C3) in this clade may be explained by hybrid speciation rather than a reversal from C4 to C3. All C3–C4 intermediates belong to a different clade that also contains C3 species, but species limits, including the widely studied A. tenella, are unclear. The clade including A. tenella and A. halimifolia contains most of the species endemic to the Galapagos whereas A. nesiotes, also endemic to the islands, is nested among widespread American taxa. This suggests that the Galapagos radiation of Alternanthera may have arisen from at least two independent colonization events followed by a subsequent radiation in the former lineage. © 2012 The Linnean Society of London, Botanical Journal of the Linnean Society, 2012, 169, 493–517.

The species are generally amphistomatic except Pandiaka heudelotii that is hypostomatic. Anomocytic and paracytic stomatal types were mostly found but cyclocytic and diacytic types may accompany, especially in Cyathula spp. The anticlinal wall pattern varies from undulate to curved and curved-straight in the family. Other useful epidermal features are peltate scales, trichomes of different types such as candelabra type, unicellular and multicellular conical types, long acicular glandular forms that may be tuberculate or non-tuberculate and the filiform type; all can be employed at species level for delimitation purpose. Sub-familial grouping of the genera is supported while monophyly and polyphyly suggested in Gomphrenoideae and Amarantheae respectively can be inferred from the extent of character variations in the species. An indented dichotomous key is presented for species delimitation. (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Borsch T., Ortuno Limarino T. & Nee M. H.: Phylogenetics of the neotropical liana genus Pedersenia (Amaranthaceae: Gomphrenoideae) and discovery of a new species from Bolivia based on molecules and morphology. — Willdenowia 41: 5–14. — Online ISSN 1868-6397; © 2011 BGBM Berlin-Dahlem. doi:10.3372/wi.41.41101 (available via http://dx.doi.org/) The monophyletic genus Pedersenia comprises eleven species in the Neotropics, one of which, P. volubilis, is here described as new to science, being an endemic of mixed semi-deciduous Bolivian-Tucuman Interandean lower subhumid forest at mid elevations of the Department of Santa Cruz, Bolivia. Among the liana species of Pedersenia, it differs by twining stems, synflorescences constituted by terminal stems of several metres and small, lanceolate leaves. It is also characterised by two synapomorphic substitutions in the matK CDS. Sequence data of trnK/matK show considerable divergence between morphologically very similar liana species of tropical evergreen bro...

Gomphrena Linnaeus (1753: 224) (Gomphrenoideae Schinz, Amaranthaceae Juss.) is a genus including about 120 species, with center of diversity in the New World, and higher species richness in Central Andes, in argentinean and bolivian Puna, and Caatinga, and Cerrado habitats in Brazil (see e.g., Muller & Borsch 2005; Sánchez del Pino et al. 2009).

The Amaranthaceae-Chenopodiaceae alliance has been the focus of several phylogenetic studies, but major questions concerning the internal relationships of Amaranthaceae still remain unanswered. This study aims to test the monophyly of the subfamily Gomphrenoideae and to examine the generic relationships within this group. Parsimony and Bayesian analyses of trnL-F and rpl16 show that the subfamily Gomphrenoideae is monophyletic. The clade of Gomphrenoideae represents a large and diverse radiation of the Amaranthaceae in the New World. Unilocular anthers are a morphological synapomorphy for Gomphrenoideae that was derived from bilocular anthers. Three major clades are resolved: the Gomphrenoids, the Alternantheroids, and the Iresinoids, which are largely supported by pollen morphology. The Iresinoid clade is sister to Alternantheroids plus Gomphrenoids, rendering metareticulate pollen as the synapomorphy for the latter two clades. Tribes and subtribes delimited by androecium and inflorescence characters are poly- or paraphyletic. Several genera are monophyletic including the large genus Alternanthera, whereas Gomphrena is polyphyletic. Irenella and Woehleria are resolved within Iresine whereas Blutaparon and Lithophila fall within the polyphyletic Gomphrena. The trnL-F and rpl16 sequence data are the most variable chloroplast regions examined to date for the family and are highly effective in resolving relationships in Amaranthaceae.

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.

A phylogenetic analysis of Chenopodiaceae and Amaranthaceae was carried out using sequence variation of the chloroplast gene rbcL. Our sampling included 108 species of these two families along with 29 species of Caryophyllales serving as outgroups. Phylogeny inferences with maximum parsimony and maximum likelihood indicate that the two families form a well‐supported monophyletic clade that is sister to Achatocarpaceae. Despite extensive sampling, we found that the relationship between Chenopodiaceae and Amaranthaceae remains unclear as a result of short and weakly supported basal branches. The clearly monophyletic Polycnemoideae (traditionally considered a subfamily of Chenopodiaceae) appear as sister to Amaranthaceae sensu stricto. Within Amaranthaceae, most major lineages inferred except Gomphrenoideae and Celosieae do not correspond to recognized subfamilies and tribes. Bosea and Charpentiera branch first in the Amaranthaceae. Within Chenopodiaceae, the genera of Betoideae occur in basal and largely un...

Jamesbondia is formally proposed here as a new subgenus of Alternanthera, a large Neotropical genus, with four species [A. costaricensis Kuntze, A. geniculata Urb., A. olivacea Urb., and A. serpyllifolia (Poir.) Urb.], mostly found in Central America and the Caribbean Islands. In a recent phylogeny using ITS, trnL-F, and rpl16 data and samples of three of the four species listed above, an unpublished genus Jamesbondia was embedded within Alternanthera. The other three species (not A. costaricensis) clustered in a clade with 97% JK support. Here to determine the position of A. costaricensis within Alternanthera and taxonomically revise the species in subg. Jamesbondia, we analyzed ITS, trnL-F, and rpl16 data from GenBank accessions for 31 species and our new molecular data for A. costaricensis to reconstruct a phylogenetic tree confirming that A. costaricensis belongs to the Jamesbondia clade (88-97% JK; 0.88-1.0 PP). Alternanthera costaricensis, Telanthera olivacea Urb., and Achyranthes serpyllifolia Poir. were lectotypified, and we document the distribution of A. costaricensis in Mexico for the first time. Insight from nomenclatural notes, taxonomic descriptions, morphological illustrations, distribution, and a key for species of Jamesbondia provided here will be used to propose a new subgeneric classification of Alternanthera.

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.

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.