19201 SARGENT, NOTES ON NORTH AMERICAN TREES. VII 117 



(in Herb, Arnold Arboretum) collected by C. L. Anderson near Santa Cruz, 

 California, with narrow pubescent leaves, a glabrous rachis and puberulous 

 branchlets, and referred by Koehne to his P. demissa var. Nuttallii f, 

 holotricha. 



Pninus virginiana var. melanocarpa, nov. comb. — Cerasus demissa var. 

 melanocarpa A. Nelson in Bot, Gaz. xxxiv, 25 (1902). Pruniis melano- 

 carpa Rydberg in Bull. Torr. Bot. Club, xxxiii. 143 (1906). 



This is the widely distributed Rocky Mountain form of the Choke Cherry, 

 differing from the eastern typical form in its rather thicker leaves and usu- 

 ally darker fruit sometimes black or nearly black at maturity. This is a 

 common usually shrubby plant often only 2^ or S° high, or occasionally a 

 tree, distributed from western North and South Dakota and Nebraska to 

 southern Colorado, New Mexico and southern Arizona to the Pacific coast 

 where it ranges from British Columbia to San Diego County, California. In 

 North Dakota the eastern and western forms **intergrade so completely 

 that there is no way of distinguishing them except in extreme cases. The 

 difference is apparently due to the conditions under which they grow, so 

 that they are to be considered merely as forms of the same species."^ 



A form with yellow fruit may be distinguished as forma xanthocarpa, n, 

 forma. Near La Veta, Huerfano County, Colorado, C. S. Sargent, August, 

 1911. 



Prunus virens Shreve. 



This New Mexican and Arizona Cherry-tree, although very closely re- 

 lated to Prunus serotina Ehrhart, may be distinguished from that species 

 by its smaller more finely serrate glabrous usually elliptic or oval to rarely 

 oblong-obovate or ovate leaves 'acute or rounded, rarely acuminate, at apex 

 and cuneate at base, by its eglandular petioles, by its shorter racemes and 

 smaller flowers. In the typical form the leaves are glabrous, but on some 

 trees the under side of the midrib of the leaves is furnished on the margins 

 below the middle with a thick coat of rusty pubescence showing the con- 

 nection of these trees with 



Prunus virens var. rufula, n. var. — Padus rufula Wooton & Standley 

 in Contrib. U.S. Nat. Herb. xvi. 132 (1913). 



Differing from the type in the rusty brown persistent pubescence on the 

 under side of the midrib of the leaves, the pubescent petioles, the pubes- 

 cence on the lower part of the rachis, the puberulous ovary, and in the rusty 

 brown pubescence of the young branchlets. 



The type of Padus rufula (No. 563998 in U.S. Nat. Herb.) collected on 

 the west fork of the Gila River, Arizona, August, 1900, has leaves only 

 4-4.5 cm. in length and branchlets thickly covered with matted rusty hairs. 

 The specimens in the National Herbarium referred to Padus rufula vary in 

 the amount of the pubescence on the branchlets, and those of No. 497841 



* H. F. Bergman, Fl. North Dakota ia Sixth Biennial Rep. North Dakota Soil and Geologi- 

 cal Survey, £07 (1912). 



