Rydberg : Notes on Rosaceae 379 



quarto of 716 pages and 20 plates, good paper and good large print. 

 The descriptions in Latin are excellent and complete. To these 

 are added elaborate discussions and notes in German. The 

 synonymy is practically complete, and the citations have nothing 

 of the vagueness so characteristic of many so-called monographs. 

 As one should expect, a comparison of Dr. Wolf's monograph 

 and my treatment of the genus in the North American Flora 

 discloses many differences; but most of these result from our dif- 

 ferent views. Dr. Wolf is exceedingly conservative both as to 

 genera and species, and the present writer has the reputation of 

 being exceedingly "radical." Dr. Wolf believes in large genera 

 and broad species, and admits numerous varieties and forms; 

 while the writer believes in small genera and narrowly limited 

 species. If the diversity of two plant forms is of any value at 

 all, the writer admits them as distinct species; if the variation is a 

 trifling one, it is simply ignored. In this way the old rank of 

 variety has been disposed of. Of course, also, many of the dif- 

 ferences arise from the fact that Dr. Wolf had no or insufficient 

 material of American plants and had to rely upon the printed 

 descriptions alone in many cases. 



While Dr. Greene seems to go too far in splitting up the genus, 

 Dr. Wolf is in my opinion too conservative. He has left Potentilla 

 with about the same limitation as Lehmann had in 1856, only 

 that he has merged even Duchesnea in Potentilla. I can not under- 

 stand why he did not treat Sibbaldia in the same way. This 

 genus is really much more related to Potentilla than Drymocallis 

 and Dasiphora are. The only distinctions given by Dr. Wolf are: 

 "Stamens 5 (very seldom 10); carpels 5-15 (the few Potentillas 

 with only 5 stamens have always numerous carpels)." But there 

 are several Potentillas that have few carpels although they have 

 10-20 stamens. The distinctions are therefore not well drawn. 

 Of course the position of the style, which I have used as a generi- 

 cally distinctive character, will place it outside of Potentilla proper 

 and in the group with Dasiphora. Dr. Wolf, however, does not 

 regard this as a generic character and therefore, if consistent, he 

 should have merged Sibbaldia into Potentilla. 



Dr. Wolf has divided the genus Potentilla into 2 sections and 

 6 subsections. These subsections are based on the differentiation 



