ORCHIDACE.E 



several exceptions they are very clearly differentiated, and as to 

 their specific characters offer no perplexing problems. The spe- 

 cies in the western United States which Dr. Rydberg referred 

 to Piperia have been variously treated, so that at present several 

 are recognized which in my studies I have not considered speci- 

 fically distinct. In Mexico the small group composed of H. cly- 

 peata, H. lactiflora, H. Schaffneri, H. jaliscana, and a few others, 

 is perplexing and later may be regarded very differently as more 

 material helps to clarify obscure relationships. That these species 

 are puzzling will be keenly felt by any student who attempts to 

 distinguish them by means of an analytical key. Almost every 

 character which at first appears to differentiate them will be 

 found occurring sporadically here and there in individuals of 

 several of the other species. The relation borne to the middle 

 lobe by the lateral lobes of the trifid labellum would have to be 

 relied on to some extent, though it is not at all constant. Yet it 

 is inconceivable that any serious student would combine these 

 species as variants of one polymorphic species. 



Up to the time of his death Mr. A. A. Eaton rendered valu- 

 able assistance toward the construction of this monograph and 

 devoted his attention to the bibliography and to the distribution 

 of the species. His notes are incorporated in the body of the 

 work and may be distinguished by the initial letters of his name. 

 His examination of the specimens preserved at Paris, which 

 were described so inadequately by Richard, proved a vast help 

 in the interpretation of obscure Mexican species. During his 

 work at the Museum d'Histoire Naturelle de Paris he obtained 

 clear photographs of all the Habenarias collected by Galeotti, 

 and identified our specimens by careful comparisons with the 

 types. Through the kindness of Sir W. T. Thiselton-Dyer, INIr. 

 Eaton and I were enabled to compare our material with the 



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