TAXONOMIC STUDY OF MACHAERANTHERA , SBCTICWS MACHAERAtfTHERA AND HESPERASTRUM (ASTERACEAE) B. L. Turner Department of Botciny, University of Texas, Austin, TX 78713 ABSTRACT The sections Machaeranthera and Hesperastrum of the genus Machaercinthera are treated systematically. The former is comprised of two species, M^ tanacetifolia and M^ tagetina . The section Hesperastrum is comprised of three species: Machaeranthera asteroides , with three varieties; M^ bigelovii , with three varieties; and M^ canescens , with ten varieties divided among two subspecies. Keys to these various taxa are provided along with distribution maps. In addition, a chromosomal review of the sections is provided which includes numerous previously unreported chromosome counts. All counts were diploid with 2n=8. One new combination, M^ canescens subsp. glabra , is proposed. The genus Machaeranthera was established by Nees in 1832. The generotype, M^ tanacetifolia , is a widespread, erect, tap-rooted, annual with lavender rays and a base chromosome number of x=4. Most subsequent workers, A. Gray for example, reduced Machaeranthera to sectional status and placed it within the broad fabric of Aster . As such, the section included several seemingly disparate elements, for excimple the lavender -rayed Machaeranthera gymnocephala , which Greene (1894) placed in his newly resurrected Eriocarpum . Hall (1928) transferred all of the latter into his broadly conceived Haplopappus , placing these into his section Blepharodon . Shinners (1950) reunited Blepharodon (including Eriocarpum ) with Machaeranthera , which he accepted as a genus distinct from Aster . Cronquist and Keck (1957), while recognizing M achaeranthera as a genus, nevertheless retained section Blepharodon in Haplopappus (sensu Hall), despite the removal of its type species, Machaeranthera gymnocephala , which, along with several other lavender-rayed taxa, was placed in the series Originales of Machaeranthera. Hartman (1976) has reviewed in much greater detail the information presented above. Indeed, after poring over his unpublished thesis for a number of years now, I find his treatment remarkably thorough and taxonomically sound. Consequently I have little hesitation in taking up the arrangement and nomenclature which he provided. Hartman treated Machaeranthera as comprizing eight sections. These were divided into two subgenera, as follows: 207
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