ORCHIDACE.E 



maintenance of broadly characterized, easily defined and quickly 

 recognized genera. 



When we turn to Pogonia as usually defined and study it in- 

 tensively, it becomes very evident that conservative systematists 

 have carried to extremes the effort to keep the genus intact. In- 

 deed, some of the subgenera are too clearly differentiated from 

 one another to allow of any doubt as to the desirability of elevat- 

 ing them to higher rank. Nervilia and Codonorchis are no longer 

 regarded as subgenera of Pogonia ; they have been transferred 

 to distinct subtribes, and there is no reason to question the treat- 

 ment that has resulted in their removal from the Pogonia alli- 

 ance. But there are other groups of species, those referred to 

 Cleistes, Psilochilus, Isotria and Triphora, that cannot be so 

 easily disposed of, and it is with regard to their treatment that 

 opinions vary. 



I propose to discuss here the subgenera of Pogonia that come 

 within the range covered by the seventh edition of Gray's Man- 

 ual and, by means of detailed plates, to make clear those charac- 

 ters that seem to be most important in considerations of generic 

 segregation of the species. 



The so-called extremists recognize Pogonia, Isotria and Tri- 

 phora, but there is no thoroughgoing discussion of the charac- 

 ters on which these genera are based, although in a paper on the 

 anatomy of our native Pogonias Theo. Holm^ indicated differ- 

 ences that he regarded as of sufficient importance to necessitate 

 the recognition of three clearly differentiated groups of species. 

 In his observations of the subterranean system oi Pogonia trian- 

 thophora he made very clear that there are morphological pecu- 

 liarities that warrant the withdrawal of this species from Pogo- 

 nia proper, and I believe for other reasons that it is wise to re- 



"^ American Journal of Science ser. 4, 9 (1900) 13-19. 



[4] 



