260 
PotenTILLA NicoiieTi (Wats.) Sheld. Bull. Geol. and Nat. Hist 
Surv. Minn. 7: 16. 1894. 
P. supina Nicollet Wats. Proc. Am. Acad. 8: 553. 1873. 
This is much nearer the European P. supina, having the same 
prostrate habit, small leaflets and falsely racemose inflorescence, 
but the achenes are of the same structure as in P. paradoxa. Only 
the basal leaves have several more or less distant pairs of leaflets; 
the lower stem-leaves have generally two approximate pairs, and 
the rest are ternate. It is a rather rare plant. The following 
specimens have been examined: 
Minnesota: C. A. Geyer (Nicollet’s Exped.), no. 361, 1838 
(type); IZssouri: B. F. Bush, 1893; /owa: Hitchcock. 
POTENTILLA RIVALIS Nutt.; Torr. & Gray, Fl. N. Am. 1: 437- 
3 1838.45 
This differs from the preceding by its upright habit, cymose 
inflorescence, small petals which are scarcely half as long as the 
sepals, and achenes without any swelling on the inner side. The 
leaves are generally pinnate with two pairs of approximate leaflets, 
except the upper ones, which are ternate. Occasionally, especially 
in depauperate specimens, all the leaves are ternate, when it is 
very difficult to separate it from the next. The range is from 
Oregon and Montana to Mexico. All specimens named P. rivalis 
I have seen from the prairie States, except one from the stock- 
yards of Chicago, belong to the following species : 
POTENTILLA MILLEGRANA Engelm.; Lehmann, Ind. Sem. Hort. 
Bot. Hamb. 1849: Add. 11. 1849. 
This, as well as P. pentandra, have been regarded as varieties of 
the preceding. I think it is better, however, to consider them 
species. In P. mllegrana all the leaves are, asa rule, ternate. The 
plant is much branched, with divergent branches and in the typi- 
cal form spreading. This habit and the smaller, nearly white 
achenes separate it from forms of P. rivalis with ternate leaves. 
The plant is generally also more glabrate. It has a wide range, 
but is not a common plant. It extends from Illinois to New 
__ Mexico, California and Washington. 
