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—Baccharis funkiae, a new species endemic to Uruguay, is described and illustrated here. We also provide field work pictures, etymology, distribution and habitat, and preliminary conservation status information. Comments on how to differentiate it from the morphologically similar B. subopposita, highlighting differences setting the new species apart are discussed. Additionally, a key to the identification of the Uruguayan species belonging to Baccharis subgen. Baccharis sect. Cylindricae is presented.

—The number and identity of species within Euthamia (Asteraceae, Astereae) have varied considerably among taxonomic treatments. Euthamia graminifolia (L.) Nutt. is often treated broadly, including plants from the northern and eastern United States and Canada, including the Atlantic and Gulf Coasts. Broad-leaved, largely glabrous plants from New Jersey to the Florida Panhandle have been inconsistently treated as E. graminifolia, E. graminifolia var. hirtipes (Fernald) C.E.S. Taylor & R.J. Taylor, E. hirtipes (Fernald) Sieren, or a hybrid between E graminifolia and E. caroliniana (L.) Greene ex Porter & Britton. Similarly, plants from the Florida Panhandle to eastern Louisiana have been incorporated into E. graminifolia or E. graminifolia var. hirtipes with only Greene in 1902 recognizing these plants as a distinct species, E. scabra Greene. To determine the identity and proper rank of these entities, morphological and phylogenetic analyses were performed to evaluate relationships within Euthamia. Plants from the Atlantic Coast most morphologically resemble Gulf Coast plants which similarly resemble E. gymnospermoides Greene. The Gulf Coast plants and E. gymnospermoides share similar DNA sequences while the Atlantic Coast plants represent a unique clade. Neither Gulf Coast nor Atlantic Coast plants contain highly polymorphic sequences, indicating that they are not hybrids. Occasional plants found within southernmost Alabama and the Florida Panhandle have polymorphic sequences and intermediate morphology however, suggesting that putative hybrids exist between Gulf and Atlantic Coast plants. This study concludes that both entities deserve specific rank as E. scabra Greene for scabrous plants along the central Gulf Coast and E. hirtipes (Fernald) Sieren for largely glabrous plants mostly along the Atlantic Coast. Ecological niche modeling indicates that precipitation, especially during summer months, and soils, namely coarse fragments and sand content, drive the distribution of these organisms, largely restricted to either side of the Apalachicola River serving as a distributional barrier.

—Doellingeria and Eucephalus form the earliest-diverging clade of the North American Astereae lineage. Phylogenetic analyses of both nuclear and plastid sequence data show that the Doellingeria-Eucephalus clade consists of two main subclades that differ from current circumscriptions of the two genera. Doellingeria is the sister group to E. elegans, and the Doellingeria + E. elegans subclade in turn is sister to the subclade containing all remaining species of Eucephalus. In the plastid phylogeny, the two subclades are deeply divergent, a pattern that is consistent with an ancient hybridization event involving ancestral species of the Doellingeria-Eucephalus clade and an ancestral taxon of a related North American or South American group. Divergence of the two Doellingeria-Eucephalus subclades may have occurred in association with northward migration from South American ancestors. We combine these two genera under the older of the two names, Doellingeria, and propose 12 new combinations (10 species and two varieties) for all species of Eucephalus.

A recent phylogenomic study has shown that Diplostephium in its broad sense is biphyletic. While one of the clades comprises 60 species distributed mainly in the Northern Andes, the clade that contains the generic type, Diplostephium ericoides, contains 48 species, and primarily inhabits the Central Andes. Here, I propose to reinstate the generic name Piofontia and transfer to it the species of Diplostephium in the Northern Andean clade. Piofontia consists, then, of 60 species of woody subshrubs, shrubs, and small trees inhabiting high Andean forests and paramos of Costa Rica, Colombia, Venezuela, and Ecuador. A morphological description is provided for the genus Piofontia along with a species list with 60 new combinations. Dysaster cajamarcensis is shown to be a synonym of Diplostephium serratifolium. Finally, a brief discussion about themorphological evolution of South American Astereae is provided.

Five species and one hybrid of Baccharis with alate stems are recognized in the northern Andes between Colombia and central Peru, of which three species are endemic. A new species, B. woytkowskii, is described from northern Peru. Two species are restricted to northern Peru, and all northern Andean species occur there. Three species also occur in Ecuador and a single species in Colombia. Baccharis subbimera is neotypified and the species endemic to the northern Andes are described and illustrated. Morphological delimitation of species is discussed, and a determination key is provided.

The systematics of subtribe Symphyotrichinae were studied with sequence data from two nuclear regions: the 18S–26S nrDNA internal and external transcribed spacers (ITS and ETS) and the 5S nrDNA non-transcribed spacer. The primary objective was to use data from these two regions to resolve relationships among Almutaster, Psilactis, and Symphyotrichum. The combined ITS + ETS data and the 5S data were subjected to phylogenetic analyses using parsimony and Bayesian methods. Both datasets identified two major clades in Symphyotrichinae: one consisting of Almutaster, Psilactis, and Symphyotrichum subgenus Virgulus, and the other consisting of most other species of Symphyotrichum, including all species of S. subgenus Symphyotrichum. In addition, there were seven instances of disagreement between the ITS + ETS and 5S results. Assessments of these incongruences suggested that there have been three occurrences of reticulate evolution, involving six species of Symphyotrichum: 1) S. tenuifolium, 2) S. morane...

The phylogenetic relationships of six out of seven genera from the informal Hinterhubera group (Hinterhuberinae) and nine other subtribes in tribe Astereae primarily with Southern Hemisphere distributions were studied using internal and external transcribed spacer region nuclear DNA (ITS and ETS) sequence data. Bayesian and parsimony analyses were conducted on both datasets, independently and combined. Topologies resulting from the ITS and combined data sets were highly congruent, while the ETS based phylogenies were poorly resolved, probably because the characters are fewer and less informative. The monophyly of the Hinterhubera group was not confirmed, nor were the monophyly of the subtribes Podocominae, Lagenophorinae, Grangeinae, and Asterinae as delimited by Nesom and Robinson. Instead, our results suggest a closer relationship among the taxa from similar geographic areas. Within the Hinterhubera group, the monophyly of the genera has been confirmed. Westoniella was sister to Laennecia (Podocominae), while Hinterhubera was sister to Laestadia and Blakiella. The radiate Diplostephium and Guynesomia were disparately placed in the southern hemisphere clade and not related to the other radiate genera of Hinterhuberinae. Present analyses suggest that dioecy in Aztecaster and Baccharidinae evolved independently as hypothesized by Nesom. Archibaccharis (Baccharidinae) was sister to Plagiocheilus (Grangeinae). The analyses of ITS and ETS data, and Bayesian analysis of the combined dataset, resolved Baccharidinae as non monophyletic. Constraint analyses forcing a monophyletic Baccharidinae, with Plagiocheilus sister to Archibaccharis, did not reject monophyly of the subtribe.

A molecular and morphological phylogenetic analysis of South American Podocominae is herein performed. Taxa of both South American and Australasian Podocominae as well as members of other subtribes of Astereae were included in the analyses. Sequence data from the nuclear internal transcribed spacer (ITS), and the plastid trnL–trnF intergenic spacer regions were used in the molecular analysis to assess relationships among the South American genera of Podocominae. The trnL–trnF intergenic spacer provided only six informative characters. In contrast, the ITS region was more variable. Our results showed that: 1) neither the South American genera of Podocominae nor the whole subtribe Podocominae are monophyletic; 2) South American and Australasian genera, initially placed in the subtribe Podocominae on the basis of morphological characters, show no evidence of close relationship in our phylogenetic analyses based on molecular data; 3) Our results do not confirm Podocoma in its current concept as monop...

South American Microgyne Less. is resurrected from the synonymy of Microgynella. Microgyne Cass. is a nomen nudum and therefore not validly published. The replacement generic name Microgynella, a homotypic synonym of Microgyne Less., is illegitimate and superfluous. A revision is presented for the two species of Microgyne, one herein described as new. The new species, Microgyne marchesiana, is described from Uruguay and is diagnosed by pinnatifid leaves, whitish pappus, and a thick testa. A neotype is designated for Microgyne trifurcata Less. Detailed descriptions and illustrations are provided for the two species, together with additional data on anatomy.

Established concepts of Chrysothamnus have been primarily based on morphological similarity or on molecular studies employing only exemplar taxa. Those investigations and treatments conceptualized Chrysothamnus as a single evolutionary unit with affinity for Ericameria, Petradoria, and Stenotus among other taxa. The hypotheses of relationship presented here are based on nuclear ribosomal 3′ ETS and ITS data that were analyzed using several optimality criteria. The results indicate that Chrysothamnus as traditionally perceived is polyphyletic, with species placed in four well-supported lineages. Three of the four clades also contain taxa from other genera. Seven species of Chrysothamnus along with Acamptopappus, Amphipappus, Hesperodoria scopulorum, Tonestus lyallii, and Vanclevea constitute one clade, while four species aggregate in another clade that includes Hesperodoria salicina, Tonestus microcephalus, and T. peirsonii. A third lineage consists of Chrysothamnus gramineus and appears distantly...

Conyza notobellidiastrum and C. rivularis are two South American species that recently were transferred to Podocoma, based mainly on corolla, style, and cypsela characters. Following evidence obtained from comparative morphological and molecular studies developed in Podocoma, Podocominae, and Astereae in general, Conyza notobellidiastrum and C. rivularis were excluded from Podocoma. A new genus, Exostigma, is described to include these two species: Exostigma notobellidiastrum and E. rivulare. Moreover, C. notobellidiastrum var. oblongifolia is placed in synonymy with. C. primulifolia, lectotypes are designated for the names Conyza notobellidiastrum and C. rivularis, and the appropriate new combinations are made. © Copyright 2012 by the American Society of Plant Taxonomists. Fil: Sancho, Gisela. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. División de Plantas Vasculares; Argentina

Intergeneric and interspecific relationships of Psilactis were studied using data from restriction site analysis of chloroplast DNA and nuclear rDNA. Molecular evidence supports the removal of Psilactis from Machaeranthera and its alliance with Aster. Within the Aster lineage, chlo- roplast DNA data support an alliance composed of members of Psilactis that have n = 4 (P. tenuis, P. boltoniae) and those of Aster subg. Oxytripolium that are based on x = 5 (A. subulatus, A. tenuifolius), separating them from the n = 9 species of both Aster and Psilactis. Evidence from nuclear rDNA, in contrast, supports different alignments by combining n = 4 and n = 9 species of Psilactis and by allying the n = 5 and n = 10 species of Aster subg. Oxytripolium with other species of Aster. Comparison of cpDNA results with evidence from morphology, rDNA, and isozymes suggests that hybridization may account for some relationships supported by chloroplast DNA. Psilactis is re-established as a distinct genus of six species, with P. mexicana placed in synonymy under P. gentryi. The following new taxonomic combinations are made: Psilactis gentryi, Psilactis odysseus, and Psilactis hetero- carpa.

Chloroplast DNA restriction site analysis was carried out on 55 taxa of tribe Astereae, including 21 species of Machaeranthera and many additional putatively related taxa. Phylogenetic analysis delineates a well supported, monophyletic Machaeranthera alliance within Astereae that includes several segregate genera of Haplopappus and all taxa historically associated with Machaeranthera except sect. Psilactis, which is allied with Aster. The Machaeranthera alliance includes a large proportion of the taxa of tribe Astereae with x = 4, 5, and 6, and contains no taxa with base chromosome numbers greater than x = 6. Chloroplast DNA data indicate five well supported monophyletic groups within the Machaeranthera alliance. One of these groups includes Xanthocephalum, Isocoma, Prionopsis, and Grindelia (all with x = 6), but does not include the x = 6 genera Xylorhiza and Pyrrocoma. A second group includes M. sect. Sideranthus and the monotypic M. sect. Stenoloba. A third group consists of M. sect. Blepharodon and two species not normally associated with the section, M. viscida and M. gypsitherma. Comparison of cpDNA evidence with one rDNA site mutation suggests that chloroplast and nuclear genomes in M. viscida, M. gypsitherma, and M. heterophylla have different origins. A fourth group includes Pyrrocoma and M. sect. Arida. In the fifth group, cpDNA data suggest a close alliance between Oonopsis and M. sects. Machaeranthera and Hesperastrum. Molecular evidence, when considered with other data, is consistent with an hypothesis of aneuploid reduction in base chromosome number from x = 6, or ascending and descending aneuploidy from x = 5 in the Machaeranthera alliance. Machaeranthera Nees consists of mostly taprooted annual or perennial herbs that are distributed in western North America. As treated by Hartman (1976, 1990; table 1), and as here defined, the genus consists of 36 species. Except for three discoid species, all have both ray and disc florets. Ray color is variable within the genus, with both xanthic (yellow) and cyanic (white, blue, pink, purple) rays present. The composition of Machaeranthera, relationships among its sections, and its affinities to other genera have been the subject of much debate (i.e., Cronquist and Keck 1957; Hartman 1976, 1990; Shinners 1950; Turner and Horne 1964; Watson 1977). Large morphological and cytological data bases exist, but synthesis of these data with evidence from hybridization, flavonoid, and micromorphological studies has not resulted in a consensus concerning the systematics of Machaeranthera. Circumscription of Machaeranthera has been extremely difficult because the closest relatives of many species that have been placed in the genus may actually be in several different genera (i.e., Haplopappus Cass., Xylorhiza Nutt., Psilactis A. Gray, and Aster L.). The task of resolving relationships within Machaeranthera is further compounded when one considers that such taxa as Haplopappus and Aster may be even more poorly understood than Machaeranthera. Hall (1928) treated Haplopappus as a large genus of 21 sections, but most or all of the North American sections may eventually be treated as segregate genera or included in other genera. Haplopappus sect. Blepharodon is the group most commonly allied with Machaeranthera. The section has included cyanic-rayed, xanthic-rayed, and eradiate species, all of which Shinners (1950) combined with Machaeranthera. Cronquist and Keck (1957), on the other hand, included only the cyanic-rayed and eradiate species of the section in Machaeranthera (series Originales, table 2). Hartman (1976, 1990) placed the eradiate and cyanic-rayed species in Machaeranthera sect. Blepharodon and the xanthic-rayed species in Machaeranthera sects. Sideranthus, Stenoloba and Havardii (table 1). Xylorhiza has been variously treated as a section of Aster, a section of Machaeranthera, or as a distinct genus. Cronquist and Keck (1957) in

Recent collections of Aster blepharophyllus A. Gray, the first since its discovery in 1851, prompted a reevaluation of its identity. It is properly placed in the genus Machaeranthera as M. gypsitherma Nesom, Vorobik, & Hartman. Within that genus, it shares characters with species of sect. Blepharodon as well as those of sect. Arida (both groups sensu Hartman), but we place it tentatively in the latter group. Of particular significance is its chromosome number of n = 5 pairs, reported for the first time, which is shared with species of sect. Arida.

Restriction site mutations analysis using 18 restriction endonucleases for chloroplast DNA's from North American Gutierrezia has led to a generic circumscription which is somewhat different from those previously proposed. Molecular data agree with a recent taxonomic treatment of Lane (1982, 1985), which transferred the x = 4 species from Xanthocephalum and submerged Greenella into Gutierrezia, but they do not support the submersion of the monotypic genus Thurovia. Thurovia is closely related as a sister group to Amphiachyris and should be resegregated from Gu- tierrezia. The study indicated that Xanthocephalum with x = 6 is very distantly related to Gutierrezia, even though Xanthocephalum has often been treated as part of the Xanthocephalum-Gutierrezia complex. Xanthocephalum is, in contrast, very closely related to Grindelia, which also has a base chromosome number of x = 6. Traditional species of Gutierrezia, G. californica, G. grandis, G. microcephala, G. sarothrae, G. serotina, and G. texana, constitute a closely related cluster and are well-separated from other purported members of the genus. Gutierrezia californica s. str. and G. bracteata should be separated again as distinct species. The herbaceous species, G. sericocarpa and G. sphaerocephala, appear to be the most primitive in the genus.

Remya (tribe Astereae) is a genus of three species endemic to the Hawaiian Islands. Until 1985, only two species, R. mauiensis and R. kauaiensis, were known. They were both thought to be extinct. Although rediscovered in 1971 and 1983, respectively, the plants are very rare and the populations endangered. A new species in the genus is described: R. montgomeryi sp. nov., known only from cliffs near the rim of Kalalau Valley, Kaua'i. The most diagnostic features distin- guishing it within the genus include complete lack of pubescence; long, thin peduncles; heads with a larger, hemispherical involucre; acute to obtuse phyllaries; and more numerous disk florets. Examination of material of all three species suggests that the heads are monoecious; the ray florets are pistillate and disk florets functionally staminate. Remya kauaiensis and R. montgomeryi differ from R. mauiensis in having dimorphic disk florets; the outer ones are smaller, have funnelform corollas, and apparently are neutral or pistillate whereas the inner ones are considerably larger, have cam- panulate corollas, and appear to be functionally staminate. Remya may be related to the Australasian genus Olearia. Remya is a small genus in the tribe Astereae. Three species can be distinguished, all endemic to the Hawaiian Islands. Two of them, R. kauaiensis Hillebrand and R. mauiensis Hille- brand, were described in 1888. Apparently nei

Tetramolopium is a genus of shrubby to suffrutescent perennial Compositae known only from New Guinea and the Hawaiian Islands. Evidence from biogeography suggests the genus was introduced into Hawaii from New Guinea recently, and perhaps originated from a single introduction. The morphological and ecological diversity of Tetramolopium in the Hawaiian Islands suggest there has been rapid divergence associated with adaptive radiation. Despite the diversity, all taxa are completely interfertile with fertile F1, F2, and F3 hybrids having been obtained. An electrophoretic study of allozymes revealed little divergence at 22 genes coding soluble enzymes. The mean genetic identity for pairwise comparisons of 19 populations from seven species is 0.95, a very high value normally obtained for conspecific plant populations. The results for Tetramolopium contrast sharply with other instances of high genetic identity between species, where taxa are similar morphologically and usually reproductively isolated. The enzyme data also support the hypothesis of recent, rapid divergence in Hawaiian Tetramolopium.

Amphiachyris is a North American genus of two species, A. dracunculoides and A. amoena. Related to Gutierrezia, it has in the past been placed in synonymy under that genus and also under Xanthocephalum. The generic status of A mphiachyris, as recognized by Solbrig, is accepted. Chromosome counts for both species and two species of Gutierrezia are reported. Counts of n = 4 for A. amoena and A. dracun- culoides and n 5 and n = 8 for G. texana are new. Preliminary chromatographic results indicate the presence of sulfated flavonoids in Amphiachyris. The genus Amphiachyris is composed of two annual species, one of which is restricted to the limestone-derived clay soils of the Edward's Plateau region of central Texas. The other, a very weedy species, is distributed widely on black prairie soils in the midwestern United States with scat- tered localities known as far east as South Carolina (Fig. 1). The distri- butions of Amphiachyris and of the annual species of Gutierrezia overlap throughout much of their ranges; these taxa are also quite similar in gross morphology. It is not surprising, therefore, that the taxonomic placement of Amphiachyris has been altered several times by various work- ers. The purpose of the present study is to evaluate the status of the taxon, using morphological, cytological and chemical methods.

Bradburia hirtella is a small annual endemic to eastern Texas and Louisiana. The species includes two cytotypes n = 3 and n = 4, the latter known from only one plant. Under cultivation an n = 4 individual existed as a short-lived perennial blooming several times over the course of 2.5 years. The two cytotypes were crossed and the 2n = 7 progeny survived and bloomed. Meiosis was studied in 2n = 6, 7, and 8 individuals. Three bivalents were typically observed in late prophase and metaphase I in pollen parent cells of 2n = 6 plants. Four bivalents were typical in the 2n = 8 plant. In meiosis in the 2n = 7 plants, bivalents and multivalents were observed. The mitotic meta- phase karyotypes were also compared. Both the 2n = 6 and the 2n = 8 plants had one large acro- centric pair and a smaller acrocentric satellite chromosome with a short arm with subequal satellite and proximal portions. The 2n = 8 plant had two small metacentric pairs. The 2n = 6 plants had only one large submetacentric pair. The presumed closest relatives are in Chrysopsis. Efforts to cross Bradburia with several species of Chrysopsis were unsuccessful. Flavonoid patterns in the two genera were similar but did not confirm or refute a close relationship. On the basis of karyotypes the n = 4 race of Bradburia appears to be intermediate between the n = 4 perennial C. mariana and the more specialized n = 4 annual C. pilosa. While B. hirtella could be transferred to Chrysopsis, the distinctive staminate disc florets of the former are considered sufficient to separate the two at the generic level.

Gutierrezia comprises sixteen North American species; two have two varieties each. Thurovia and Greenella are congeners of Gutierrezia, five taxa formerly of Xanthocephalum are mem- bers of Gutierrezia, and G. argyrocarpa is a distinct species. Characteristics shared by all taxa include alveolate receptacles that are pubescent with uniseriate trichomes that are swollen medially and long-attenuate apically, disc corollas that are clavate or funnelform and glabrous (except in one species), disc style-branch appendages that are linear with penicillate collecting hairs, achenes that are clavate or cylindrical and pubescent, and a pappus of scales that are united and/or greatly reduced in some taxa. In North America, the genus is distributed from the area of Mexico City northward throughout the Sierras Madres Occidental and Oriental, the central plateau of Mexico, and the central and western United States northward to western Canada. Habitats are well-drained, high montane slopes, mesic or semi-arid grasslands, and deserts.

Chaetopappa elegans, a narrow endemic from the White Mountains of south-central New Mexico, is unusual in Chaetopappa because of its double pappus of numerous bristles and narrow scales, comparatively long, lanceolate stylar appendages, crinkled stem pubescence, alveolate receptacle, faint cypsela nerves, long ligules, and occurrence on granitic rock. Its chromosome number is 2n = 9, In habit it resembles C. hersheyi from the nearby Guadalupe Mountains, but characteristics of the head are more like those of C. bellioides and C. pulchella from north-central Mexico and the Big Bend region of Texas, and Leucelene ericoides, widespread in arid southwestern North America. In its alveolate receptacle it resembles some species of Aster and the West Coast genus Pentachaeta, whereas its double pappus is reminiscent of some species of Erigeron and Aster (sect. Ionactis). The crinkly stem hairs are like those of some Erigeron species. A portion of the front ranges of southcentral New Mexico, the White and Sacramento mountains, form a continuous north-south oriented chain about 130 km long. The northern, primarily igneous portion, the White Mountains, rises to about 3660 m on Sierra Blanca, the southernmost glaciated peak in North America. The southern portion of the chain, the Sacramento Mountains, are primarily limestone and are considerably lower, barely exceeding 2740 m. This small mountain chain is isolated from other mountain ranges in the Southwest by fairly broad low gaps of arid grassland or desert, gaps that serve as barriers to migration of montane vegetation. To the north and south these gaps are relatively small and not particularly low (cf. map on p. 34 in Patterson 1980). During elevational fluctuation of vegetation in the late Pleistocene (Van Devender and Spaulding 1979) these gaps were narrowed even more and were, therefore, even less of a barrier to vegetation migration. On the one hand, the isolation of these mountains has produced an area of comparatively high endemism for New Mexico, while on the other the isolation has not been so complete that the vegetation has sharply differentiated. Plants from the higher elevations are mostly conspecific with those to the north; plants from lower elevations find their congeners mostly to the south. Most endemics in these mountains apparently have diverged but slightly from ancestral stock and show patterns of relationship similar to that of the general composition of the vegetation with which they are associated. The new species described herein adds one more endemic element to the White Mountains, one that is associated with a small genus of more southern affinity. Species of Chaetopappa are found in the mountains, hills, and plains in and surrounding the arid grassland regions of the northern portion of the Mexican Plateau, extending onto the southern Great Plains as far north as Kansas. This new Chaetopappa is unusual in that it occurs on granitic rocks at relatively high elevations, whereas its closest relatives all occur well to the south and then on limestone. It is also unusual in a number of morphological features. Shinners (1946a) redefined Chaetopappa to include a number of smaller genera previously distinguished by pappus differences. The publication of C. plomoensis B. Turner (Turner 1977) added a new kind of pappus to the genus. Our new species, with its pappus of numerous bristles and scales, further adds to pappus types known in the genus. In addition, it has stylar appendages, stem hairs, and a receptacle unique in Chaetopappa but similar in these characteristics to at least some species in Pentachaeta, Aster, and Erigeron. The faint nerves of the cypsela of C. elegans contrast to the prominent nerves on all other Chaetopappa. Chaetopappa elegans Soreng & Spellenberg, sp. nov. (fig. 1).-TYPE: U.S.A., New Mexico

Reports suggesting that the basic chromosome numberfor Aster section Heterophylli is x = 9 have been cited to support the hypothesis that x = 9 is the ancestral basic number for the whole genus. The present report gives chromosome counts for 35 populations in ten species, nine of which are traditionally placed in section Heterophylli. The chromosome numbers in 33 populations present a polyploid series of n = 8, 16, 24, and 32. Reinterpretation of photomicrographs by Avers (1954) lends additional support to the finding that the basic number for the section is x = 8 rather than x = 9. If counts for the three species not yet re-examined agree with these results, the balance between species of the x = 8 and x = 9 groups will be significantly shifted, and phylogenetic considerations based on the number of species belonging in each of the three "modes" (x = 5, 8, and 9) in the genus must be reassessed. Inasmuch as all Old World species of Aster exhibit x = 9, this group remains the largest on a worldwide basis, but with the inclusion of section Heterophylli, the x = 8 group comprises the largest number of species in North America, the generally acknowledged center of origin for the genus. The presentfindings are interpreted as supporting the hypothesis that evolution proceeded from the low basic chromosome number of x = 4 or 5 rather than the high one of x = 9. Aster is one of the relatively few members of the tribe Astereae that exhibits more than one mode of chromosome numbers, namely x = 5, 8, and 9. Several publications dealing with the phylogeny of the tribe are concerned with the question of which of the basic chromosome numbers is primitive, the high x = 9 or the low x = 4 or 5. Authors in favor of the hypothesis that the high number is ancestral (Huziwara, 1959, 1967; Raven et al., 1960; Solbrig, 1967; Solbrig et al., 1964, 1969) point out that the majority of species have the base number of x = 9 whereas x = 5 is found in a much smaller number of rather heterogeneous species adapted to arid regions and saline habitats. They reason further that the high base number is usually correlated with some other characteristics considered primitive in the Asteraceae, such as perennial and often somewhat woody habit and a high degree of polyploidy. In the view of these authors, Aster species with x = 5 chromosomes have been derived through successive aneuploid loss and subsequent catastrophic extinction of the less successful intermediate types-i.e., taxa with x = 6 or 7. The opposite stand is taken by Turner et al. (1961), who reason that 1I thank Christine A. Newell for checking some of my chromosome counts. 2 Botany, University of Illinois at Urbana-Champaign, Urbana IL 61801.

The eight taxa of Xanthocephalum, including X. durangense, X. gymnospermoides var. intermedium, and X. gymnospermoides var. eradiatum, are characterized by glabrous recep- tactes. goblet-shaped, pubescent disc corollas, deltate style branch appendages with short, rounded collecting hairs, and essentially glabrous achenes with very little or no pappus. The taxa are dis- tributed in damp, generally montane valleys from central Mexico northwest through the Sierra Madre Occidental to southern Arizona and western Texas. The chromosome number of all species is n = 6. Two natural interspecific hybrids are known. Xanthocephalum has affinities with other entities of Astereae that have x = 6, particularly Grindelia and Olivaea. Xanthocephalum has recently been reduced in number of species via the transfer of five taxa

Aster breweri is a rayless, high montane Californian species first described as Chrysopsis breweri and placed in C. subg. Ammodia (=Heterotheca sect. Ammodia). It has always been considered to be related to the goldenaster Heterotheca oregona (synonym: C. oregona) because both lack the well developed short outer pappus whorl and yellow rays typical for Heterotheca. However, Aster breweri has the diagnostic hair and phyllary traits of Aster sect. Eucephalus, not those of Heterotheca. Critical are its smooth-surfaced woolly hairs, lacking the tuberculae typical of Heterotheca. Chrysopsis breweri var. multibracteata is placed in synonymy under Aster brickellioides (including A. siskiyouensis). New combination: Aster breweri. Brewer's aster (basionym: Chrysopsis breweri A. Gray (1866); synonym: Heterotheca breweri (A. Gray) Shinners (1951)) was found to be unlike the true goldenasters (Compositae: Astereae) of the genus Heterotheca in that it lacked knobs on the osteolate cells of the uniseriate hairs (Sem

Xanthocephalum, Gutierrezia, Greenella, Gymnosperma, Amphiachyris, and Thurovia have been variously treated with regard to their generic limits by several authors in the last 3 decades. The generic delimitation presented here is based on a thorough re-evaluation of all 26 known North American members of these genera. The data obtained in the study strongly support the following disposition of the taxa, which differs from all previous treatments. Xanthocephalum (x = 6), a genus of montane areas in western Mexico and the southwestern United States, contains five species (one with three varieties) and is more closely related to Grindelia and Olivaea than to Gutierrezia and its allies. Gutierrezia (x = 4) encompasses seventeen specific and infraspecific taxa in North America, including not only the eight taxa recognized for it by Solbrig, but also five taxa formerly of Xanthocephalum, and the genera Greenella and Thurovia (the last resulting in Gutierrezia triflora, comb. nov.). The genus thus constituted ranges from central Mexico north and west through the central and western United States to Saskatchewan. Amphiachyris (n = 4 or 5) with two grassland species of Texas and central United States, and the monotypic Gymnosperma (x = 8), which ranges from northern Guatemala to Texas and westward to Arizona, are closely allied to Gutierrezia. The taxonomic problem presented by the group of genera that unfortunately have been called the "Xanthocephalum complex" is one of generic rather than specific circumscription. The genera concerned, besides Xanthocephalum, are Amphiachyris, Amphipappus, Greenella, Gutierrezia, Gymnosperma, and Thurovia. Taxonomic histories have been provided by Solbrig (1960a, 1960b, 196 1a, 196 1b, 1966), Ruffin (1974), Porter (1943), and Lane (1979, 1980b). A very brief summary of the several evaluations is as follows. A number of workers, including Bentham (1873) and Gray (1852, 1853, 1880a, 1880b, 1883), recognized the affinity of most of these genera, but for the most part maintained them as distinct entities. Shinners (1950) united all except Amphipappus and Thurovia under Xanthocephalum. Solbrig (1960b) again segregated them, while Ruffin (1974, 1977a) recommended that Gutierrezia and Greenella be submerged in Xanthocephalum and that Amphiachyris, Amphipappus, Gymnosperma, and Thurovia be considered distinct. It might seem unnecessary to reconsider this taxonomic problem in view of the several treatments already in the literature. However, data that have accumulated even since the most recent of these suggest that such a reconsideration is in order. None of the previous studies included every species of each genus; further, the various authors changed only the taxonomic rankings of whole, historically constituted genera. I wished