554 PROCEEDINGS OF THE AMERICAN ACADEMY 



acute ; petals suborbiculai', emarginate, 2" long, about equalling the 

 calyx ; stamens usually 25 ; carpels numerous. — With scarcely a 

 doubt to be referred to P. sericea. The species are kept distinct by all 

 Russian botanists, though Regel & Herder state that the only apparent 

 distinction is in the larger flowers of P. sericea, and that this is proba- 

 bly but the large-flowered alpine form of P. Pennsylvanica. — Found on 

 the coast of Maine and New Hampshire, and in British America from 

 Canada to the Rocky Mts., and rather common southward in the 

 mountains to Colorado and New Mexico. It is occasionally somewhat 

 resinous, especially upon the calyx, and sometimes the achenia. 



Var. strigosa, Lehm. Stems 6-12' high; silky-tomentose 

 throughout, the upper surface of the leaves scarcely less so ; leaflets 

 deeply pinnatifid, margins of the narrow lobes revolute ; cyme short 

 and close. — From Wisconsin and the Saskatchewan to Kansas, and in 

 the mountains to New Mexico. The var. bipinnatijida, Torr. & Gray, 

 is merely a form with the elongated linear segments usually more 

 spreading. 



Var. glabrata. (P. sericea, var. glabrata, Lehm.) "Leaves sub- 

 glabrous on both sides, the lobes of the leaflets silky-tufted at 

 the apex." — Rocky Mts. of British America (Drummond). 



7. P. Hookeriana, Lehm. Densely white-tomentose and villous, 

 the leaves greener above ; stems 3-5' high ; leaflets three, cuneate- 

 ovate, 5 - 8" long, incised nearly to the midvein, the middle one shortly 

 petiolulate ; flowers short-pedicelled, in dense cymelets on the slender 

 branches ; calyx very silky-villous, the narrow bractlets equalling the 

 acute sepals ; petals obcordate, 1J-2" long, equalling or exceeding the 

 calyx ; stamens 20. — British America. Specimens collected by 

 Bourgeau on the Saskatchewan accord with Lehmann's description and 

 figure. 



8. P. pulchella, R. Br. Dwarf, arctic, silky-villous and tomen- 

 tose ; stems 1-4' high, 1 - 3-flowered, slender, naked; leaves pinnately 

 3-5 foliolate, the ovate leaflets 3 - 6" long, coarsely cleft nearly to the 

 midvein, the linear-oblong lobes divaricate ; bractlets broad, equalling 

 the sepals ; petals obovate or obcordate, 2" long, equalling the calyx ; 

 stamens 20. — Arctic America and Greenland (Parry ; Kane ; 

 Hayes). 



II. Styles filiform, not glandular at base ; inflorescence cymose. — 



Spec. 9-29. 

 * Style terminal (or nearly so in P. brevifolia) ; carpels glabrous, 



