380 Rydberg : Notes on Rosaceae 



of the styles. It is practically the same character as I used in 

 distinguishing the genera, only that I placed more importance 

 on the position and Dr. Wolf on the form of the style. I also 

 took the stamens into consideration, which Dr. Wolf only in- 

 cidentally mentions. Dr. Wolf's Rhopalostylae correspond 

 to my genus Dasiphora. His Nematostylae correspond to 

 Sibbaldiopsis and Comarum, together with several groups not 

 American and therefore not treated by me. These two subsections 

 constitute his section Potentillae trichocarpae. It is evident 

 that Comarum (Potentilla palustris of his monograph) should not 

 be counted in this section, as the carpels are perfectly naked. 

 He associates P. palustris, a herbaceous plant with creeping root- 

 stock and glabrous achenes, with P. Salesowiana, a shrub with 

 hairy achenes. While the latter is in its right position in the sys- 

 tem, the former is not. I shall discuss this further under the 

 genus Comarum. To Dr. Wolf's Potentillae gymnocarpae 

 belong the rest of the subsections. Closterostylae correspond 

 to the genus Drymocallis and Leptosty^lae to Argentina. The 

 subsections Conostylae and Gomphostylae show so many inter- 

 gradations, a fact admitted by Dr. Wolf, that there is no ground, 

 in my opinion, for keeping them apart. They constitute what 

 I have called Potentilla. In the main points Dr. Wolf and myself 

 agree, the only difference being that what he calls subsections, 

 I call genera. I can not help, however, but accuse Dr. Wolf of 

 inconsistency, for Sibbaldia, Fragaria, Horkelia, Comarella, and 

 Stellariopsis, all admitted by Dr. Wolf, are none of them better 

 genera than these subsections. 



Now let us take up the different groups of Potentilla in the 

 order they are in the North American Flora. 



Tormentillae 

 This contains six species, of which two, Potentilla reptans and 

 P. procumbens, are introduced. Dr. Wolf admits only one North 

 American species, regarding P. pumila and P. simplex as varieties 

 of P. canadensis. Potentilla caroliniana was evidently unknown 

 to him. Regarding P. pumila, he states that I regarded it in 

 1898 as a distinct species but withdrew the rank in 1899 (re- 

 fering to the Bulletin of the Torrey Botanical Club for that year, 



