1920] SIIERFF^-BIDENS 95 



ever since. s In 1901, Greene (Pittonia 4:242-270) presented the 

 results of a study of Bidens. He commented upon the dissimilarity 

 between such species as B. cernua L. and B. tripartita L. Even so 

 radical a botanist as he, however, refrained from proposing a generic 

 segregation of the B. cernua forms. Nevertheless, Greene did 

 segregate the aquatic Bidens Beckii as the type of a new genus, 

 Megalodonta; and, when the peculiar achenes of this species arc 

 considered, it seems wise to accept Greene's new genus as valid. 



Strangely enough, no one appears to have tried to segregate 

 generically the pronounced and well denned group of Bidens species 

 typified by the species Bidens reptans (L.) G. Don. 6 These species 

 differ from the more typical species in being climbers, and in having 

 long flat achenes that are hispid along the two edges in such a way 

 at times as to suggest a centipede. Again, my own Bidens mirabilis 

 (Bot. Gaz. 61:496. pi. 31. 1916), with achenes flat, strongly 

 constricted above into a thick neck and crowned with even 8-10 

 aristae, might be segregated as the type of a new genus. Similarly, 

 the anomalous Bidens clarendonensis Britton, with trailing, some- 

 what woody stem, and thick, rhombic-ovate leaves, would be inter- 

 preted by some as representing a new genus. 



Thus it is seen that, if we accept the narrow concept of Bidens 

 held by Cassini, Lessing, and Hillebrand, and seek to segregate 

 the native Pacific species under the name Campylotheca, to be 

 consistent we shall have to subject the entire genus Bidens to a 

 process of subdivision and segregation, resulting in some six or 

 eight genera. There are at least two good reasons for not adopting 

 such a course. In the first place, the accuracy of such a series of 

 interpretations is not so well established as to justify overturning 

 almost the entire nomenclature of the genus. In the second place, 

 the lines of demarcation among the various subordinate groups are 



s In the herbaria Bidens oslruthioides is the universally used name. It is inter- 

 esting to note that a closely similar form was described by Klatte as Bidens guale- 

 malensis (Bot. Jahrb. 8:44. 1887). x\nother related form, apparently more clearly 

 distinct, however, was placed by Bentham in Bidens and described as B. costaricensis 

 (Benth. ex Oerst., Kjoeb. Vidensk. Meddel. 94. 1852). 



6 De Candolle (Prodr. 5:599. 1836), however, did create the name Bidens 

 Coreopsidis for one of these species. And, even earlier, the names Coreopsis reptans 

 L., Coreopsis incisa Ker.,etc, had been given to certain of these species, but without 

 very serious consideration being given to their generic affiliations. 



