38 KKY TO THE SPECIES 



4. Potentilla concinna Rich. (Early Potentilla). Low, spreading, many 

 stemmed ; leaves white tomentose, especially beneath ; leaflets 5, obovate, deeply 

 toothed ; petals obcordate, exceeding the sepals and bracts. Warm gravelly 

 slopes and plains ; early spi'ing. 



5. Potentilla pulclierrima Lehm. (.Beautiful Potentilla). Stems slen- 

 der, 3-6 dm. high ; leaves green and silky -pubescent above, white with tomentum 

 beneath, long petioled except the smaller stem-leaves; leaflets mostly 5, oblanceo- 

 late or broader, crenate ; the obovate, emarginate petals nearly equaled by the 

 acuminate sepals. Frequent in meadows and grassy valleys. 



9. DRYMOCALLIS 



Erect, glandular- pubescent or viscid herbs, with pinnate leaves ; stamens 

 25-30 ; style thickened and glandular below and attached near the base of the 

 achene. Otherwise much as in Potentilla. 



1. Drymocallis fissa (Nutt.) Rydb. Very leafy, stems several, 15-30 cm. 

 high, glandular hairy, viscid in the crowded cyme ; leaflets about 4 pairs, orbicu- 

 lar or rhombic, cleft and serrate ; petals orbicular, bright yellow, about 1 cm. 

 long. Very abundant in rocky canons. 



2. Dryxnocallis arguta (Pursh) Rydb. Taller and stouter, 3-8 dm. high, 

 brownish hairy, clammy above ; leaflets 7-1 1, oval or ovate, serrate, downy beneath ; 

 flowers white or yellowish, in an upright close cluster j stamens mostly 30. An 

 eastern species extending into the foothills of the Colorado Mountains. 



10. GEUM (A YENS) 



Herbs with pinnately compound or lyrate leaves, a bell-shaped or flattish 

 5-cleft calyx, numerous achenes crowded on a prominent receptacle' and with the 

 long persistent styles forming hairy or naked tails. 



1. Geuin strictum. Ait. (Yellow Avens). Hairy-pubescent, erect, rather 

 stout, branched above, 4-10 dm. high; leaflets wedge-ovate, the terminal one large; 

 receptacle of fruit downy; styles bent and jointed near the middle, the upper part 

 deciduous, the lower naked and hooked, becoming elongated. Meadows and mar- 

 gins of copses. 



2. Geum macrophyllum Willd. (Large-leaved Avens). Similar, more 

 bristly hairy; the long root-leaves with terminal leaflets large, suborbicular-cor- 

 date, the lateral small or minute ; receptacle nearly naked. Moist creek banks 

 and bottom lands. 



11. SIEVERSIA (Avens) 



Like Geum, but with stem-leaves reduced or bract-like, the styles wholly per- 

 sistent and not jointed, and the calyx lobes erect instead of reflexed. 



1. Sieversia ciliata (Pursh) Rydb. (Long-plumed Avens). Densely soft- 

 pubescent ; stems scapose, 1-2 dm. high ; leaflets very numerous, small ones 

 interposed among the larger, obovate, cut-toothed leaflets ; flowers 3 or more, on 

 long peduncles ; calyx and corolla both purplish ; styles long and plumose in fruit. 

 Frequent on stony slopes. 



2. SieTersia turbinata (Rydb.) Greene (Rocky Mountain Avens). Green, 

 slightly pubescent above : leaflets ovate or wedge-shaped, 3-lobed or entire ; tube 

 of calyx turbinate ; the yellow, sub-orbicular petals exceeding the calyx lobes ; 

 styles glabrous. Very abundant on wet slopes in the higher mountains. 



