11 
Mexican species: P. Lhrenbergiana, Haematochrus, fusca, and com- 
arwides,a few Indian species, as for instance P. Nepatensis and 
P. atosanguinea, and two species of the Southwestern United 
States, viz. : 
POTENTILLA THURBERI A. Gray, Mem. Am. Acad. (II) 5: 318. 
1854. 
As described by Gray and Lehmann, P. 7hurberi should be per- 
fectly green and only slightly hairy. Such specimens have been 
collected as follows: 
New Mexico: Thurber, no. 1107, 1851; Dr. Henry, 1854; Dr. 
Bigelow (Mex. Bound. Surv.), no. 347, 1851; E. L. Greene, 1880; 
E. Palmer, 1869. Arizona: Lemmon, 1881; C.G. Pringle, 1884; 
Wooton, 1895. 
More than half of the specimens in our collections that are 
labelled P. Thurberi do not agree with the original description, and 
I take them to represent an undescribed species : 
V POTENTILLA ATRORUBENS. 
Potentilla Thurberi Rothrock, Wheeler Surv. 4: 113. (mainly.) 
1878. 
Stem 4-7 dm. high, finely pubescent and with scattered long 
villous spreading or reflexed hairs; stipules ovate or lanceolate, 
1-2 cm. long, often toothed ; basal and lower stem-leaves long- 
petioled, digitately 5—7-foliolate, glabrous or slightly silky above, 
silky and white-tomentose beneath; leaflets obovate to oblance- 
olate, coarsely serrate; stem-leaves sessile, 3—5-foliolate; cyme 
Open and branched; flowers about 15 mm. in diameter; calyx 
silky-villous and finely pubescent, about 1 cm.in diameter; bract- _ 
lets lanceolate, often equalling the lanceolate-triangular, more or > 
less acuminate sepals; petals dark reddish purple, very broadly 2 
obcordate, exceeding the sepals; stamens 20. (Plate 288.) v 
This species much resembles ?. 7iurberi,from which it has not _ & 
been distinguished. {t differs, however, in several characters that 
seem to be fairly constant, viz., the tomentum on the lower surface 
of the leaves, the much sharper dentation, the long silky spread- | 
ing or reflexed hairs of the stem and calyx, and generally more ae 
acuminate sepals. [From the Mexican P. fusca and P. comarioides 
it differs in the leaflets, which are serrate to the very base. Itseems — 
to be more common than P. 7hurberi and has about the same range. — 
_ Arizona: Rothrock, no. 399, 1874; C. G. Pringle, no. 305, 
1881; 1884; no. 1,578, 1887; M.E. Jones, 1884; J. G. Lemmon, 
