70 MONTANA AGRICULTURAL COLLEGE SCIENCE STUDIES. 



Potentilla nivea Altiaca, Rydberg, Mon. Pot. 86. Flat-top Mtn., 

 Teton Co., 7000 ft., July 5, 1897, R. S. Williams. 



Potentilla Norvegica, L. This narrow-leaved, rugose fruited 

 form seems more common here than the villous, wider-leaved P. 

 Monspdiensis, L. 



Bozeman, Sept. 22, 1897; Kalispell, Sept. 8, 1899; Billings, June 



Potentilla Pennsylvanica strigosa, Pursh. Eastern plains main- 

 ly. Rocky Canyon, Bozeman, May 26, 1900; Big Coulee Cr., Sweet 

 Grass Co., June 15, 1901; Wibaux, July 9, 1901; Stanford, July 5, 

 1901, F. A. Spragg, 217; N. Boulder, Jefferson Co., June 25, 1899, 

 C. D. Flaherty. 



Potentilla rhomboidea, Rydberg, Bull. Torr. Bot. Club, 23 1248. 

 Ridge above Bannock, 7000 ft., July 19, 1880, S. Watson, 114 (Gray 

 Herb.). 



*Poterium annua, Nutt. In waste places, well established at 

 Arlee, Aug. 5, 1901. 



Prunus emarginata, Rydberg, Flora, 477, is P. trichopetala^ 

 (Greene) below. 



Prunus trichopetala, (Greene) ; Ccrasus trichopetala, Greene, Proc. 

 Biol. Soc. Wash. 1905 ; Prunus emarginata, Rydberg. Columbia Falls,. 

 May 28, and Aug. 20, 1894, R. S. Williams, 1005. 



Prunus Virginiana, L. Various authors have referred this 

 species to Montana by including in it P. demissa, W f alp. and this is 

 even followed by Sargent (Sylva, 4:42), though he enumerates the 

 chief points of distinction. The two are perfectly distinct as 

 species and need never be confused even in the herbarium. P. 

 demissa is a shrub or small tree, rarely attaining a diameter of 5 

 inches, the young twigs are usually more slender, the leaves are 

 smaller, thicker, paler beneath, less acuminate and with the tips of 

 the teeth normally somewhat incurved and the fruit is smaller 

 (16 mm.), sweet and edible when ripe, though slightly bitterish and 

 astringent. The latter is the common "choke cherry" in Montana, 

 but the true P. Virginiana occurs in some localities west of the 

 Divide as a good-sized tree 8-10 inches in diameter. The twigs are 

 thicker and it has larger, thinner more acuminate leaves, with 

 straight or salient teeth, and larger fruit. 



Columbia Falls, Sept. 6, 1892, R. S. Williams; Plains, June 6, 1902. 



