398 MISC. PUBLICATION 42 3, U. S. DEPT. OF AGRICULTURE 



4. Herbage not conspicuously villous; leaflets thin, sparsely pubescent to 



glabrate above, the terminal one obovate; inflorescence dense or 

 rather open; sepals at an thesis 4 to 6 mm. long„ 3. P. glandulosa. 

 3. Plants acaulescent or nearly so, not viscid (5). 



5. Plants without runners; leaves green on both faces, digitately 3-f olio- 



late; leaflets cuneate-obovate, 3- to 5-dentate at the truncate apex; 

 petals ochroleucous or pale yellow, shorter than the sepals; stamens 



usually 5: Section Sibbaldia 4. P. sibbaldi. 



5. Plants with runners; leaves silvery-sericeous at least beneath, pinnately 

 multifoliolate with much smaller leaflets interspersed with the large 

 ones; leaflets oblong, elliptic, or obovate, coarsely toothed; petals 

 bright yellow, much longer than the sepals; stamens numerous: 



Section Argentina 5. P. anserina. 



1. Styles terminal or nearly so (6). 



6. Stamens 5, inserted at a considerable distance from the base of the receptacle 

 and from the pistils; pistils 1 to 5; leaves pinnate; hypanthium with a 

 flat or saucer-shaped peripheral expansion, on which the stamens are 

 inserted; leaves elongate, narrow, with very many small leaflets; stems 

 erect, 30 cm. long or longer: Section Ivesia, Comarella (7). 

 7. Leaflets cleft at apex; petals dark purple 6. P. multifoliolata. 



7. Leaflets parted or divided; petals yellow 7. P. sabulosa. 



6. Stamens seldom fewer than 10, inserted close to the pistils, these 5 or more: 



Section Eupotentilla (8) . 



8. Petals rose red or dark red; plants caulescent; stems erect or nearly so, 



seldom less than 30 cm. long; basal leaves with 5 to 7 leaflets, digitate 



or nearly so 8. P. thurberi. 



8. Petals yellow (9). 



9. Inflorescence usually many-flowered, conspicuously leafy, its leaves not 

 bractlike although usually smaller than the other stem leaves; plants 

 annual or biennial; flowers inconspicuous, the petals seldom surpass- 

 ing the sepals; styles short, fusiform; leaves digitate or the lower ones 

 pinnate with a short rachis; leaflets coarsely toothed or shallowly 

 cleft (10). 

 10. Petals not much shorter than the sepals; achenes commonly finely 

 rugose; hairs of the stem mostly rather stiff, long, and spreading 

 or widely ascending; leaves all 3-foliolate or the lower ones 



pinnately 5-foliolate 9. P. monspeliensis. 



10. Petals much shorter than the sepals; achenes usually smooth; hairs 

 of the stem soft, mostly short and subappressed (11). 

 11. Branches erect or ascending at a narrow angle; cymes elongate, 

 racemiform; pubescence partly glandular; leaves all digitate, 



trifoliolate 10. P. biennis. 



11. Branches spreading or ascending at a wide angle; cymes not 



racemiform; pubescence not glandular 11. P. rivalis. 



9. Inflorescence few-flowered or, if many-flowered, then not conspicuously 

 leafy, its leaves mostly much reduced; plants perennial; flowers 

 commonly showy; petals usually surpassing the sepals (12). 

 12. Basal leaves pinnate, the rachis elongate (except in P. pulcherrima) ; 

 plants caulescent; inflorescence several- to many-flowered (13). 

 13. Leaves at base of the plant bipinnate, the primary divisions 

 parted or divided into linear, lanceolate, or oblanceolate lobes; 

 pubescence strigose or villous; flowering stems decumbent, 

 seldom more than 20 cm. long; cymes few-flowered; pedicels 

 elongate, slender, often somewhat arcuate; bractlets nearly 

 equaling the ovate-lanceolate, acuminate sepals; petals consider- 

 ably longer than the sepals 12. P. plattensis. 



13. Leaves at base of the plant simply pinnate, the primary divisions 

 at most coarsely toothed (14). 

 14. Leaflets shallowly toothed toward the apex, usually entire below 



the middle 13. P. crinita. 



14. Leaflets deeply toothed or cleft more than half of their length, 

 usually nearly to the base; stems seldom less than 25 cm. long; 

 inflorescence open, often many-flowered; petals distinctly sur- 

 passing the sepals (15). 

 15. Basal leaves obscurely pinnate, the rachis very short (3 to 8 

 mm. long) ; leaflets 5 to 9, crowded, green above, usually 

 conspicuously white-tomentose as well as sericeous beneath. 



14. P. PULCHERRIMA. 



