Rydberg : Notes on Rosaceae 377 



Even if there were no structural differences in the flowers of Ar- 

 gentina and Potentilla (which, however, exist), there are not even 

 any essential habitual differences between P. canadensis, P. sim- 

 plex, and P. pumila on one hand, and P. reptans, P. procumbens, 

 and P. Tormentilla on the other. 



Dactylophyllum Spenner* was a merging of Potentilla, Fragaria, 

 Sibbaldia, etc., without any real type. 



The types of Chamaephyton, Dynamidium, and Ilypargyreum 

 Fourr.f are Potentilla supina L., P. verna L., and P. argentea L., 

 respectively. Fourrier also proposed several other genera, of 

 which Drymocallis was adopted by me for P. rupestris, P. glan- 

 ditlosa, and their allies. The rest of Fourrier's genera are not 

 represented by American species. Whether they should be re- 

 garded as distinct genera or not, can be decided only by further 

 study, and was out of the scope of the North American Flora. 



The monotype of Potentillopsis Opi? is Potentilla pentandra 

 Engelm. 



Tridophyllum NeckerJ has no type. It was based on the 

 trifoliolate species of Potentilla L., of what book of Linnaeus 

 Xecker does not state under Tridophyllum; but on page 94 we 

 find that he had in mind the 14th edition of the Systema. This 

 mattered little, however, in this case, because this division of 

 Potentilla remained unchanged from the first edition of the Species 

 Plantarum to the 14th edition of the Systema, the first and the 

 last of the works of Linnaeus that Necker possibly could have had. 

 The group contained P. monspeliensis, P. norvegica, P. nivea, 

 P. grandiflora, and P. subacaulis. Only the two first belong to 

 Tridophyllum, as modified by Dr. Greene. § He states: "Among 

 all segregated genera that have been proposed, not one is better 

 entitled to the rank of a genus than Necker's Tridophyllum. As 

 its name indicates, it is founded upon species of Linnaean Poten- 

 tilla having trifoliate leaves. But this mark of the foliage is not 

 one which is considered essential. He makes the generic rank 

 of the group to rest on the very small ovaries, greatly reduced 

 styles and minute naked achenes. The so-called Potentillas that 



*F1. Frib. 1084. 1829. 



tAnn. Soc. Linn. Lyon II. 16: 371. 1868. 



JElem. 2: 93. 1790. 



§Leaflets 1: 188. 1905. 



