POTENTILLA ATRORUBENS.
Potent/I/a Thurber/ Rothrock, \Vheeler 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 I cm. in diameter ; bract lets lanceolate, often equalling the lanceolate-triangular, more or less acuminate sepals ; petals dark reddish purple, very broadly obcordate, exceeding the sepals ; stamens 20. (Plate 288.) This species much resembles P. Thnrberi, from which it has not been distinguished. It 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 ing or reflexed hairs of the stem and calyx, and generally more acuminate sepals. From the Mexican P. fusca and P. an/tar/aides
it differs in the leaflets, which are serrate to the very base. It seems to be more common than P. Thurben'and has about the same range. Arthona Rothrock, no. 399, 1874 ; C. G. Pringle, no. 305, 881 ; 1884 ; no. 1,578, 1887 ; M. E. Jones, 1884 ; J. G. Lemmon, no. 2699, 1882 ; 1892; E. A. Mearns, no. 5o, 1887 ; T. E. Wilcox. 1893. New Mexico H. H. Rusby, no. 128, 1881.
The are a natural group, perhaps worth generic rank. The plant is propagated by true runners as in Fragari a. The style is lateral as in that genus and the achene large with thick corky shell. These characters are not found in any other species of Potentilla, at least not in America. All the species belonging here have pinnate leaves more or less white silky, at least beneath. The species of the group are P. ansoinoides of New Zealand and the following: