308 BOTANICAL GAZETTE [april 



"achaeniis . . . apice setuloso-ciliatis calvis vel aristulis i vel 

 2 brevissimis erecto — vel patenti — vel etiara recurvo — uncinulatis 

 onustis saepe vero nudis . . . ; indeed, the plant might almost as 

 well be considered a Bidens, but the habit is that of Coreopsis"). 

 In referring the latter species to Coreopsis, he relied mainly upon 

 its habital similarity to other (so-called) species of Coreopsis 

 from Africa. But, as will be seen presently, some of these species 

 belong in reality to Bidens. Therefore, this habital similarity, 

 affording formerly an apparently good reason for the name Core- 

 opsis Taylori, can no longer be given much consideration. 



The present writer, in bringing together the numerous species 

 of Bidens for monographic treatment, has come to adopt fully the 

 generic limits of these two genera as followed by recent American 

 botanists. In brief, the genus Coreopsis is maintained primarily 

 because of the peculiar habit and winged achenes of the Linnaean 

 type species (excluding C. alba, C. Bidens, and C. alternifolia, Sp. 

 Plant ed. i. pp. 907-909. 1753; cf. Britton, Bull. Torr. Bot. Club 

 20:280. 1893). Similarly, the genus Bidens is maintained pri- 

 marily because of the peculiar habit, strongly barbed awns, and 

 wingless achenes of several of the Linnaean type species of Bidens. 

 Among the species of either small group a fair degree of uniformity 

 in several characters occurs. But on extending our observations 

 to other species of Coreopsis and Bidens, we find remaining no 

 absolute uniformity in even one distinctive character. However, 

 one such character does persist to a surprising extent. It is the 

 presence (in Coreopsis) or absence (in Bidens) of two lateral wings 

 upon the mature achene. Among so many species from widely 

 remote regions does this character separate two genera with differ- 

 ent aspects that, in cases where other criteria are absent, it appears 

 to offer the only logical basis of distinction. Accordingly, and 

 with a view to thus delimiting these two genera more accurately, 

 notably among the African species (where the generic limits tend 

 to overlap) this basis of distinction is here adopted. As a conse- 

 quence, it is found necessary to make the following transfers for 

 the flora of Africa. This list includes only those species upon the 

 types or other positively authentic material of which I have per- 

 sonally examined the mature achenes. 



