A NEW SPECffiS OF, AND OBSERVATIONS ON, THE GENUS SMALLANTHUS (ASTERACEAE -HELIANTHEAE) B.L. TURNER Department of Botany, Univ. of Texas, Austin, TX 78713, U.S.A. The well-known genus Polymnia L. was treated by Wells (1965) as comprised of 19 species, most of which were confined to Mexico, Central and South America. Robinson (1978), following the suggestions of earlier workers, redefined the genus, restricting Polymnia to but 2 species endemic to the eastern U.S.A. and adjacent Canada; the remainder of the species were positioned in Smallanthus Mackenzie. Indeed, Robinson (1981) was so certain of the phyletic distance between the two taxa that he erected the monotypic subtribe Polymniinae to house Polymnia , positioning Smallanthus in the subtribe Melampodiinae. While I cannot subscribe to his subtribal views, careful examination of the characters emphasized by Robinson, and comparison of these with yet other characters of related genera, strongly suggests that 2 genera are envolved. At least they are as distinct from each other as are the genera Trigonospermum (base chromosome number, x = 15) and Si gesbeckea (x = 15), and it might be that Polymnia stands as close to the latter two genera as it does to Smallanthus (x = 16 or 8?), the latter of which appears as close to Rumfordia (x = 24 or 8?) is it does to Polymnia . In any case, we will treat Smallanthus as a good genus in our forthcoming treatment of the Asteraceae of Mexico (Turner & Nesom, in prep.). In the present study of Smallanthus I have had occasion to consider the relationship of S^ uvedalius of the southeastern U.S.A. (Wells, 1965) to that of L maculatus . which has heretofore been treated as a distinct species of Mexico and Central America. After examination of numerous specimens throughout the range of both taxa, I conclude that there are no characters, or combination of characters, that will adequately separate them. Wells used achene size to distinguish between these (achenes greater than 5 mm long and 4 mm wide in S. uvedalius . versus less that 5 mm long and 4 mm wide in S^ maculatus ). But achene size is a very inconstant character and varies throughout the range of the putative species. In fact, while both Blake (1917) and Wells (1965) recognized several varieties under these two species. I cannot recognize but a single variable species, as shown in Fig 1. This conclusion is nicely affirmed by Wells who comments upon the presence of 3 varieties of Smallanthus uvedalius on the island of Bermuda, all apparantly derived from a single introduction from the mainland sometimes between 1883-1905. He states, "Thus the presence of three varieties there probably must be explained by mutation or segregation in the island". Clearly the morphological expressions of this species are easily shifted, given novel conditions. In my opinion, the submergence of the names concerned is long overdue. 405
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