MEMOIRS FEOM THE DEPAETMENT OF BOTANY OF COLUMBIA UNIVEESITY 31 



mentose, pinnate, with 3-13 pairs (in P. Drummondii sometimes only ] or 2 pairs) of 

 coarsely toothed or dissected leaflets. Petals yellow or white, obcordate. Style long and 

 slender, generally filiform. 



The relationship of the group is with the Aureae, Leucopliyllae and Brevifoliae. 



Leaves dissected to near the midrib. 



Leaf-segments narrowly linear ; fruiting calyx abruptly reflexed. 90. P. millefolia. 



Leaf-segments oblong to linear ; fruiting calyx not abruptly reflexed. 

 Stem less than 1 dm. high, erect, with 1-3 small leaves. 



Leaflets with 7-9 divergent segments. 91. P. Arizonioa. 



Leaflets with 3-5 (seldom 7) ascending segments. 92. P. pinnatisecta. 



Stem leafy, over 1 dm. high, decumbent or ascending. 93. P. PlaUensis. 



Leaves not dissected to near the midrib. 

 Leaflets 2-8 pairs. 



Stem decumbent, seldom ascending, leafy. 93. P. Plattensis. 



Stem erect or ascending, few-leaved. 



Stem villous with spreading hairs. 94. P. RioJiardii. 



Stem not villous with spreading hairs. 



Leaflets less than 2 cm. long ; calyx silky-strigose. 95. P. Cascademis. 



Leaflets over 2 cm. long ; calj^x hirsute. 96'. P. Drummondii. 



Leaflets 8-13 pairs. 97. P. multijuga. 



§ ig. ARENICOLAE. 



Plant originally described as an annual but root evidently perennial or at least bi- 

 ennial. There is, however, no rootstock or woody caudex as in the species of the pre- 

 ceding group. The flowers are white and the receptacle is beset with bristles that exceed 

 the ovaries in length ; the style is long and slender, a little thickened and glandular near 

 the base. The species composing to the group was first described as an Ivesia, but the 

 numerous pistils, form of the petals and especially the position of the stamens makes it 

 a typical Potentilla. The form of the leaves is that of the preceding group. 



A single species. 98. P. Newberryi. 



§ 20. LEUCOPHYLLAE. 



Rather stout perennials. Leaves pinnate, with ■ 3-6 pairs of leaflets, grayish or 

 whitish hairy, generally densely silky, villous or tomentose especially beneath, coarsely 

 toothed or incised, but not dissected. Petals obcordate, longer than the sepals. Pistils 

 sometimes few ; style filiform. 



The relationship is with the MuUijugae and Multifidae. 



