MEMOIRS FROM THE DEPARTMENT OP BOTANY OF COLUMBIA UNIVERSITY 191 



Bootia Big. Fl. Bost. Ed. 2, 351. 1824. Not Necker. 



Potentilla subg. Clostcrostyles Torr. & Gray, Fl. N. Am. 1: 445. 1840. 



DrymocaUis Fourr. Ann. Soc. Linn. Lyon (II.) 16 : 371. 1868. 



Hypanthium saucer-shaped or hemispheric. Bractlets, sepals and petals 5. Petals 

 obovate, elliptic or nearly orbicular, neither unguiculate nor emarginate, yellow or white. 

 Stamens 20-30 in 5 festoons on the much-thickened margin of a pentagonal disk around 

 the receptacle ; filaments filiform ; anthers oblong, truncate at both ends or cordate at 

 the base, fiat and dehiscent by a longitudinal marginal slit. Receptacle hemispheric or 

 semiellipsoid with very numerous pistils. Style nearly basal, in all our species except 

 two thickened and glandular a little below the middle and tapering to both ends, rather 

 persistent ; stigma minute. Seed attached near the base of the style, ascending and 

 orthotropous. 



The genus consists of about 18 or 20 more or less glandular or viscid, erect and 

 generally rather tall herbs, with perennial rootstocks and pinnate leaves. Potentilla ru- 

 pestris L. of Europe and northern Asia, P. macrocalyx of the Pyrenees and P. geoides of 

 Siberia and perhaps a few others also belong here. The following are North American. 



KEY TO THE SPECIES. 



Style fusiform, less than twice as long as the achene. 

 Petals and sepals erect or spreading in anthesis. 

 Petals white, or in drying often yellowish. 



Plants 3-10 dm. high; cyme contracted or narrow; petals scarcely exceeding the sepals. 

 Leaves densely pubescent; branches of the cyme short. 1. D. arguta. 



Leaves more glabrate, branches of the cyme longer, erect. 2. D. convallaria. 



Plant 2-5 dm. high; cyme open with slender spreading branches; petals exceeding the 

 sepals by a third. 3. D. pseudorupestris. 



Petals yellow; sepals lanceolate to ovate, acute. 



Bractlets more than half as long as the sepals; plants evidently glandular or viscid. 

 Flowers 15-20 mm. in diameter; petals exceeding the sepals by about a third. 

 Plant tall, 3-10 dm. high; cyme open, flat-topped. 4. Z>. glutinosa. 



Plant low, 2-3 dm. high; cyme narrow. 5. D. fissa. 



Flowers 10-15 ram. in diameter; petals equalling or slightly exceeding the sepals. 



6. D. glandulosa. 

 Bractlets less than half as long as the sepals; plants scarcely at all glandular or viscid. 

 Cyme with erect or merely spreading branches ; inflorescence and hypanthium 

 densely pilose. 

 Petals slightly exceeding the sepals. 7. D. Hanseni. 



Petals exceeding the sepals by a third. 8. D. Ashlandica. 



Cyme with divergent branches; whole plant sparingly hairy, or glabi-ate. 



9. D. glabrata. 



