Sub-class 2. DICOTYLEDONES. 
Order 19. SALICALES. 
Family 35. SALICACEAE Lindl. Willow Family. 
Bracts incised; disk cup-shaped; stamens usually io or more; stigmata elongated 
and expanded; winter buds with several scales. i. Populus. 
Bracts entire; disk reduced to i or more small glands; stamens less than io, 
usually 2 ; stigmas short, not expanded; winter-buds with one scale each. 
2. Salix. 
1. POPULUS L. Poplar, Cottonwood, Aspen. 
Petioles strongly flattened laterally. 
Leaf-blades suborbicular, acute or very short acuminate. i. P. tremuloides. 
Leaf-blades broadly deltoid or cordate, abruptly long acuminate. 
Teeth of the leaves few, less than io on each side; cup of the pistillate 
flowers 6-8 mm. broad; pedicels equalling or exceeding the capsule. 
2. P. Wislizeni. 
Teeth of the leaves many, more than io on each side; cup of the pistillate 
flowers less than 6 mm. broad; pedicels shorter than the capsule. 
3. P. occidentalis. 
Petioles terete or nearly so. 
Petioles half as long as the blade or longer; blades ovate or rhombic, abruptly 
long-acuminate. 4. P. acuminata. 
Petioles about one-third as long as the blades or less; blades lanceolate, not 
abruptly acuminate. 5. P. angustifolia. 
1. Populus tremuloides Michx. In open woods and on mountain sides from 
Newf. to Alaska, Tenn. and Nev.—Alt. 6000-10,000 ft.—Near Georgetown; 
Cheyenne Canon; dry rocks, Cheyenne Mountain; Minnehaha; chaparrel- 
covered hills southeast of Ouray; South Park; near Pagosa Peak; South 
Cheyenne Canon; Colorado Springs; Ojo; foot-hills, Larimer Co.; Chicken 
Creek, West La Plata Mountains; Rist Canon; Fort Collins; Redstone; 
Howe’s Gulch. 
2. Populus Wislizeni (S. Wats.) Sarg. In canons and on river banks from 
Tex. to Colo, and Ariz.—Alt. 4000-9000 ft.—River bottoms, Arboles; Grand 
Junction; plains, Colorado Springs. 
3. Populus occidentalis (Rydb.) Britton. (P. deltoides occidentalis Rydb.; 
P. angulata Port. & Coult.; not Ait.) In* river valleys and hillsides from 
Sask. to Mont., Kans. and Ariz.—Alt. 4000-7000 ft.—Plains near Denver; 
Walsenburg; Palisade; near Boulder; Lyons; Fort Collins; along the Arkan¬ 
sas River, Lamar; Eldora to Baltimore. 
4. Populus acuminata Rydb. On river bottoms and in canons from the 
Black Hills of S. D. to Ida., N. M. and Nev.—Alt. 4000-6000 ft.—Fort Col¬ 
lins; Walsenburg; Denver; Hardin’s ranch; Redstone. 
5. Populus angustifolia James. In canons and along streams from N. D. 
to Wash., N. M. and Calif.—Alt. 6000-11,000 ft.—Pike’s Peak; Upper Platte; 
plains near Denver; South Cheyenne Canon, Colorado Springs; Gunnison; 
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