32 MEMOIRS FROM THE DEPARTMENT OF BOTANY OF COLUMBIA UNIVERSITY 



Leaves wliite-tomentose, especially beneath. 



Leaves silky as well as tomentose ; bractlets nearly equalling tlie acute sepals; 



branches erect. 99. P. Hippiana. 



Leaves tomentose on both sides ; bractlets shorter than the acuminate sepals; 

 branches spreading. 

 Stem ascending, not very slender. 100. P. effusa. 



Stem erect, very slender ; pistils few. 101. P- Coloradensis. 



Leaves more or less white-wooly on both sides. 102. P. Breweri. 



Leaves grayish silky. 



Stem stout, erect, 6-7 dm. high ; leaflets obovate, oblong, coarsely serrate. 103. P. ambigens. 

 Stem 1-4 dm. high, leaflets cuneate or linear-oblong, toothed at the apex only. 



Stem ascending or decumbent ; leaves conduplicate ; pistils numerous. 104. P. crinita. 

 Stem erect; leaves flat; pistils 5-12. 105. P. Lemmoni. 



§ 21. CANDICANTES. 



Consists of only one Mexican species, in mahy respects resembling the MuUijugae, 

 but with densely silvery-white pubescence. 

 A single species. 106. P. candieans. 



§ I. HAEMATOCHRI. 



I. Potentilla Thurberi Gray. 



PotentiUa Thurberi Gray, Mem. Am. Acad. (II) 5 : 318. 1854. 



Lfehm. Ind. Sam. Hort. Hamb. 1854: 10; Otto's Gartenz. 10: 459, Eev. Pot. 92; 

 Torr. Bot. Mex. Bound. Surv. 64; Wats. Proc. Am. Acad. 8 : 561 ; Rothrock, in U. S. 

 Geog. Surv. 4 : 113 (partly); Eydberg, Bull. Torr. Bot. Club, 24 : 11. 



Illustrations: Plate 2, f. 1; staminiferous disk, /. 2; pistil, /. 3; stamens, /. i 

 and 5 ; fruiting hypanthium and calyx, /. 6. 



Stem ascending, 3-7 dm. high, finely pubescent and sometimes somewhat villous. 

 Stipules large, 1-2 cm. long, broadly ovate, coarsely toothed. Basal and lower stem 

 leaves long-petioled, digitately 5-7-foliolate, glabrate or slightly silky, thin, sometimes 

 slightly paler beneath but not tomentose. Leaflets obovate, 3-5 cm. long, coarsely 

 toothed with broad teeth, almost crenate. Upper stem leaves sessile, 3-5-foliolate with 

 oblong leaflets ; cyme open and branched. Flowers about 15 mm. in diameter. Hypan- 

 thium puberulent, in fruit about 1 cm. in diameier. Bractlets lanceolate, about equal- 

 ling the triangular acute sepals. Petals nearly orbicular, emarginate, exceeding the 

 sepals, dark reddish purple. Stamens 20, the inner 5 with thicker filaments and 

 borne on a ring-like thickening of the disk. Pistils numerous. 



