MEMOIRS FEOM THE DEPARTMENT OF BOTANY OF COLUMBIA UNIVERSITY. 



trum by Schur.^ As the group has no representative in America, except, perhaps, P. 

 ovalis of Mexico, I have not made any attempt to investigate the vahdity of the genus. 



SprengeP suggests that a genus Trichothalamus ought perhaps to be made of the Po- 

 tentillae, which have a long-hairy receptacle, and ends his list with P. tridentata. As 

 the other species enumerated have terminal styles and are herbaceous, and Lehmann^ has 

 taken up Trichothalamus as a generic name for P. lignosa, it is not available for P. triden- 

 tata. Trichothalamus Lehm. was changed to Lehmannia by Trattinnick.* 



Bigelow'^ proposed the genus Bootia for P. arguta. In my opinion that species, to- 

 gether with about a dozen others, represents a genus quite distinct from Potentilla, but, 

 unfortunately, Bootia of Bigelow is antedated by Boottia of Necker. 



Chamisso during his collecting in California found a plant, nearly related to Poten- 

 tilla, but apparently distinct enough to constitute a genus by itself It Avas described by 

 him and Schlechtendal in Linnaea'' under the name Horkelia Californica. The genus 

 was merged into Sibbaldia by Sprengel ' but soon taken out again. It has generally been 

 regarded as a good genus by American botanists. 



Thirty years later Torrey and Gray** found that H. Gordonii and another undescribed 

 species lacked some of the essential characters of Horkelia, being intermediate between 

 it and Potentilla and Sibbaldia, and established the genus Ivesia. As the number of dis- 

 covered species increased, the generic lines between these four genera became more and 

 more indistinct, especially as three good Potentillae were described and kept in Ivesia, 

 for what reason, I do not know. This led Bentham and Hooker^ to unite Potentilla, 

 Horkelia, Ivesia and Comarum in one genus. This treatment was followed by Baillon^" 

 and by Greene." 



Tourreau^^ published in 1868 a catalogue of the plants that grow spontaneously 

 along the course of the Rhone, and, in this catalogue, he divided Potentilla {Sibbaldia 

 and Comarum excluded) into eight genera, viz., Fraga, Trichothalamus, Dynamidium, 

 Tormentilla, Ghamaephyton, Drymocallis, Hypargyrium and Potentilla. He gave no de- 

 scriptions nor any reason for the division, but merely cited the species belonging to each. 

 In Potentilla he had only one species, P. Anserina. As that species was removed from 

 Potentilla by Lamarck, we are not obliged to adopt any of Tourreau's generic names for 

 the large group of true Potentillae and rename about 200 species. The only one of his 



1 Enum. PI. Trans. 187. 1866.* 



2 Anl. Kent. d. Gew., Ed. 2, 2 : 864. 1818. 



3 Nov. Act. Nat. Cur. 10 : 585. 1821.* 

 *Eos. Mon. 4 : 144. 1834.* 



^Fl. Bost. Ed. 2, 351. 1824. 

 62: 26. 1827. 



'Syst. 4: part 2, 341. 1827. 



« Pac. E. Rep. 6 : 72. 1857. 



s Gen. Plant, 1 : 621. 1867. 

 '" Hist, de Plantes, 1 : 369. 1869. 

 "Pittonia, 1 : 95. 1887. 



'2 Ann. Soc Linn. Lyon, (II) 16 : 302-404. 1868. 



