20 MEMOIRS FROM. THE DEPARTMENT OF BOTANY OF COLUMBIA UNIVERSITY 
POTENTILLA L. 
Potentillla L. Sp. Pl. 495. 17 
Tormentilla L. Sp. Pl. 500. 1 
Quinquefolium Tournf. ; Adans. Fam. 2: 295. 1763. 
Pentaphyllum Gaertn. Fruct. 1: 349. 1788. 
Tridophyllum Neck. Elem. 2: 93. 1790. 
Fraga La Peyr, Hist. Abr. Pl. Pyr. 287. 1813. 
Trichothalamus Sprengel, Anl. Kent. d. Gew., Ed. 2, 2: 864. 1818. 
Dactylophyllum Spenn. FI. Frib. 3: 1084 (in part). 1829. 
Potentillopsis Opiz, in Lotos, 7: 380. 1857. 
Fragariastrum Schur, Enum. Pl. Trans. 187. 1866.* 
Chamaephyton Tourr, Ann. Soc. Linn. Lyon (II) 16: 571. 1868. 
Dynamidium Tourr. 1. ¢. 
53. 
759. 
Hypargyrium Tourr. 1. ¢. 
Hypanthium concave, mostly hemispheric. Bractlets, sepals and petals 5 (some- 
times 4), the latter deciduous, obcordate, obovate, rotund or cuneate, as a rule not un- 
guiculate, obtuse or emarginate, yellow, white or dark purple. Stamens most commonly 
20, in three series, viz., 10,5 and 5 respectively, sometimes more, sometimes fewer, in- 
serted not very far from the receptacular column ; anthers generally more or less didy- 
mous ; filaments filiform or subulate, not flattened or dilated. Receptacle hemispheric 
or conic bearing numerous pistils (in P. Lenmonit only 5-10, in a few others 10-20). 
Style often long and filiform, often short and thickened at the base, always attached 
near the apex of the ovary, articulated to it and deciduous. Seeds inserted near the 
base of the style, pendulous and anatropous. 
Potentilla comprises over 200 species, distributed throughout the colder part of the 
north temperate zone, extending far into the arctic, and through alpine regions of the 
tropics and South America. There is a great variation as to size and general habit 
within the genus ; some species attain a height of half a meter or more, while others are 
only a few centimeters in height. The leaves are pinnate as well as digitate, sometimes 
even in the same species, and the number of leaflets vary from 8 to 27, but are not im- 
bricated in any of the North American species. 
As the genus is very large, and very variable as far as the organs of vegetation are 
concerned, I have tried to divide it into natural groups, named from a representative 
species. As the groups are often confluent and some species could be placed with almost 
equally good reason in two groups or more, the key to these groups, as well as to the spe- 
