84 S M I T H S O S I A N C O N T R I B U T I O N S TO B O T A N Y
is the same as that seen without striations in the typical members of the subtribe Peritylinae. Ex- amination of a series of L. microglossa indicates the character is stable within a species. Attempts to correlate with the groups of Ornduff (1966) show the first type of wall in sections Baeria, Platycarpha, Ptilomeris, and one species of Burrielia. T h e second wall type is in sections Hologymne, Lasthenia, and another species of Burrielia. Only in section Bur- rielia has hybridization been reported by Ornduff between species shown here to have different wall types, and those hybrids were sterile.
T h e variation in the achene wall in Lasthenia can be compared also with the results of the detailed study of the flavonoid pigments in the genus (Bohm et al., 1974). T h e first type of achene wall, the Perityle-type, is found in groups with the most highly developed anthochlor chemistry as well as those with the nonanthochlor flavonoid patuletin. T h e second wall type is found in species which have less complex anthochlors or species with no specialized flavonoids. In the flavonoid study, the species with anthochlors are regarded as primitive within the genus, and the species without anthochlors are considered derived. As such, the Perityle-type of achene wall would also be primitive within the genus. It is notable that neither the Ornduff sections, the flavonoid types, nor the achene wall types correlate completely. It is notable, also, that anthochlors and Perityle-type achene walls are not found in the other genera of the Baeriinae, and they almost certainly are not primitive in the subtribe. Just as the anthochlors do not seem to reflect close relation to the Cor- eopsidinae, the evenly deposited phytomelanin of the achene wall does not seem to reflect a direct relationship of Lasthenia to Perityle.
FIGURES 20 1-2 10.-Chaenactidinae-Gaillardiinae-Marshalliinae: 20 1, Peucephyllum schottii A . Gray, achene, X 8; 202, Chaenactis douglasii Hook. 8z Am., achene, X 8; 203, Thymopsis thymoides Griseb., achene, X 17; 204, Arnica cordifilia Hook., disk achene. X 8; 205, Psilostrophe tagetina (Nutt.) Greene, ray floret with persistent corolla, X 12: 206, Baileya multiradiata H a w . Br Gray, ray floret with persistent corolla, X 12; 207, Trichoptilium incisum (A. Gray) A. Gray, achene, X 12; 208, Psathyrotes annua (Nutt.) A. Gray, achene, X 12; 209, Helenium autumnale L . , disk achene, X 17; 210. Marshallia graminlfolia (Walt.) Small, achene, X 17.
86 SMITHSONIAN CONTRIBUTIONS T O BOTANY
prismatic, obcompressed in Bartlettia, walls car- bonized, with or without additional pattern of knoblike thickenings, with striations; cells of seed coat usually not ornamented, with weakly annu- lated walls in Psathyrotopsis; pappus of bristles, awns, or squamellae, in l-many series, with or without differentiated central costa, sometimes with long vascular trace. Pollen 27-40 pm in diameter.
T h e subtribe is predominantly North Ameri- can with most genera in the western United States, Mexico, or Central America. A few species of Bahia and Schkuhria occur in western South America. T h e poorly understood and perhaps improperly assigned genus Thymopsis is endemic to the West Indies. Mallotopus is in eastern Asia, and Arnica extends from North America into Eu- rope. A number of species of Hypericophyllum occur in Africa.
T h e genera of the Chaenactidinae can be di- vided roughly into two groups on the basis of the endothecial cells of the anthers. T h e series of genera that includes Bahia, Achyropappus, Espejoa, Florestina, Hynienoth rix, Hypericophy llum, Pa la foxia, Plapschkuhria, and Schkuhria has mostly short en- dothecial cells in regular rows with well-defined transverse walls. T h e group shows some general trends toward smooth surfaces on the ray corollas and more strongly nerved pappus elements. T h e pappus elements often contain vascular traces, the capillary pappus in Hypericophyllum is some- times vascularlized to 2 / 3 its length, and Palafoxia has awns with veins more than half the length.
T h e achenes of the group usually show a regular pattern of knoblike thickenings in the carboniza- tion at full maturity.
T h e typical group of the Chaenactidinae, which includes Arnica, Arnicastrum, Chaenactis, Cha- maechaenactis, Hulsea,Jamesianthus, Mallotopus, Oro- chaenactis, Peucephyllum, Psathyrotopsis, and W h i t - neya, has elongate, often elliptical endothecial cells that are not in distinct rows and are pointed at the ends. T h e pappus in the group is mostly more delicate, with little or no central costa and no vascular trace. Arnica, Chaenactis, and Chamaechaen- actis have hairs on the base of the style, a character
found elsewhere in the family only in the tribe Eupatorieae. Genera in the group have carboni- zation of the achene wall lacking any additional pattern of knoblike thickenings.
Two subtribes, the Bahiinae and Chaenactidi- nae, could be recognized on the basis of the foregoing alignment, but a few genera included in the present concept do not fall easily into either of the two groups. One of these singularly dis- tinctive genera is Venegasia, which is unique in the stalked glands on the anther filaments. Another genus, Bartlettia, has the only truly obcompressed disk achenes in the tribe outside of the Coreopsi- dinae-Fitchiinae group. Thymopsis, a reduced West Indizn genus, is placed in the subtribe with reservations, but it has striate prismatic achenes, distinctly petiolate leaves, and usually single thickenings on the endothecial cells.
T h e typical element of the Chaenactidinae seems closely related to the next subtribe, Gail- lardiinae, as indicated by the reports of helenan- olide sesquiterpene lactones in Arnica (Evstratova et al., 1971; Poplawski et al., 1971). T h e carbon- ized versus uncarbonized achene wall is the char- acter by which the two subtribes are distinguished here. This character receives its most severe test in the genera Psathyrotes and Psathyrotopsis. These two genera share a strikingly distinctive pappus form, and they have been treated as parts of a single genus in the monograph by Strother and Pilz (1975), but they recognized cytological, geo- graphical, and some structural differences be- tween the two elements. T h e two genera were listed separately by Nordenstam (1977). The pres- ent study shows that the genus Psathyrotopsis of the Chihuahuan region has corollas glandulifer- ous throughout, corolla lobes with biseriate bi- lobed hairs on the outer surface and evenly dis- tributed papillae on the inner surface, anther appendages that are ovate and glanduliferous, style branches that are haired abaxially to the base, achene walls that are carbonized, and cells of the seed coat that are ornamented with annu- late thickenings. Psathyrotes of the Sonoran and Great Basin regions has corollas that are glabrous below, corolla lobes with uniseriate hairs outside
NUMBER .>I 87 and long papillae forming a marginal fringe in-
side, anther appendages that are spathulate and without glands, style branches that are haired only at the tips, achene walls that are not carbon- ized, and cells of the seed coat that are not ornamented. T h e two genera may yet prove closely related, but no character except the pap- pus has been found to suggest this. For the pres- ent, the two are placed in separate subtribes.
Psathyrotopsis is a member of the Chaenactidinae, whereas typical Psathyrotes is placed in the Gail- lardiinae close to Trichoptilium.
T h e African Welswitschiella Hoffm. has not been seen in this study, but the conventional placement is near Hypericophyllum.