A STUDY OF RHUS GLABRA 1 73 



species of the east and south, are excluded as having hardly 

 half of the " 11-31 " leaflets. 



In Britton's Manual of 1901 is that of Gray somewhat ampli- 

 fied and therefore less safe. Here Gray's evasive term, 

 " pointed," gives place to the more definitive word " acumi- 

 nate," but this excludes yet another set of forms in which no 

 leaves are acuminate. Moreover, leaves and leaflets have dif- 

 ferent ways of being acuminate, in so much that, in order to be 

 able to really describe the apex of the leaflet in each segregate 

 of R. glabra, I find it necessary to use such truly definitive 

 terms as subulate-acuminate, cuspidate-acuminate, and such 

 phrases as slenderly acuminate and caudately acuminate. But 

 more unfortunate still is the Britton's Manual description of the 

 leaves as being dark-green above. That indeed applies to what 

 I take for real R. glabra, and to several of its Atlantic slope 

 allies ; but it holds good in not one of those far-southwestern 

 species of New Mexico, Arizona and Utah, which said Manual 

 goes far out of its way to speak of as forming a part of R. 

 glabra. Even in the middle west and far-northwestern districts 

 not a tithe of the definable species can be said to have leaves of 

 other than a dull lightish green. 



Finally, the authors of none of the books knew anything of 

 the differences of fertile inflorescences in this aggregate. That 

 these in the fruiting and mature state are narrowly oblong in 

 a few, oblong-fusiform in many, and almost or quite exactly 

 pyramidal in many more, a discovery the importance of which 

 will not be disputed, is a fact which is herein first brought to 

 notice. 



It is my belief that even the flowers in some species will be 

 found to present characters available for the further establish- 

 ment of species here. Both calyx and corolla are far from 

 being the same in all ; but I have declined to make any use of 

 these for the reason that in the herbaria exist such multitudes of 

 specimens that are in flower only, and of which the fruiting 

 panicles are yet unknown. 



In true Rhus glabra, and also in by far the greater propor- 

 tion of the segregates herein proposed, both branches and foliage 

 are wholly glabrous. In the diagnoses I permit this to be taken 



