552 PROCEEDINGS OP THE AMERICAN ACADEMY 



smaller ; petals suborbicular, 3 — 4" long, white, yellowish, or in some 

 western specimens bright yellow ; stamens mostly 30, with dark thick- 

 ened anthers. — From New England to the Saskatchewan, and in the 

 Rocky Mts. from Northern Idaho to New Mexico. 



2. P. glandulosa, Lindl. (P. Jissa, Nutt. ; P. Wrangeliana, 

 Fisch. & Mey.) Resembling the last, but usually more slender and 

 branched, 1-2° high, and for the most part less pubescent ; leaflets 

 more frequently 5 - 9, usually V long or less; cyme panicled, with 

 elongated branches and more slender pedicels ; flowers often smaller ; 

 calyx much less tomentose, becoming less rigid ; bractlets linear ; 

 petals yellow, sometimes white ; stamens usually 25. — Washington 

 Territory to California, and eastward to the mountains of Colorado and 

 New Mexico. A very slender form with but few small flowers and 

 sometimes but 20 stamens, the cyme often close, is found in the Sierra 

 Nevada and in Colorado. 



* * Style terminal ; disk not thickened ; flowers small, yellow ; 

 leaves pinnate or ternate. 



f Annual or biennial ; leaflets incisely serrate, not white-tomentose ; 

 stamens 5 -20. 



3. P. Norvegica, L. Erect, stout, £-2° high, leafy, at length 

 dichotomous above, hirsute ; stipules large, ovate, coarsely incised or 

 entire ; leaves ternate, mostly short-petioled ; leaflets obovate or oblong- 

 lanceolate, 1-3' long ; cyme leafy and rather loose ; calyx large, be- 

 coming 3 — 5" long, the bractlets nearly equalling or exceeding the 

 sepals ; petals shorter, obovate, emarginate ; stamens 15, in two rows, 

 rarely 20 ; achenia rugose or nearly smooth ; receptacle large, oblong. 

 — From Labrador and the Northern States to Washington Territory, 

 Alaska, and Pt. Barrow, and in the Rocky Mts. southward to New 

 Mexico ; sparingly introduced in the Southern States. P. Labra- 

 dorica, Lehm., is but an unusually smooth form. 



4. P. rivalis, Nutt. More slender, usually diffusely branched, 

 even from the base ; pubescence softly villous, spreading, sometimes 

 nearly wanting ; stipules lanceolate to ovate, entire or toothed ; leaves 

 pinnate, with two pairs of closely approximate leaflets, or a single pair 

 and the terminal leaflet 3-parted, the upper leaves ternate ; leaflets, 

 ovate or oblong-cuneate or lanceolate, 1 - 1^' long, more or less incised- 

 serrate ; cymes loose, less leafy, with slender pedicels ; bractlets and 

 sepals equal, l£-3" long; petals minute; stamens 10-20; achenia 



