SALICINE.E. (WILLOW FAMILY.) 339 



densely flowered, the males more slender : scales short, broad-ovate, silky : 

 capsules ovate-conical, sessile, tomentose : style none, lobes of the stigmas 

 bifid. A procumbent shrub rising 2 to 3 feet above the rocks or boulders 

 over which it spreads, making a dense mass 4 to 10 feet in diameter. Old 

 Marias Pass, Montana, alt. 6 to 8,000 feet, Sargent Sf Canby. Also in Canada 

 and Labrador. 



16. S. reticulata, L. Leaves obovate or elliptic, to 1 inch long, 

 rounded at base or mostly subattenuate into a long and slender petiole, quite 

 entire, glabrous, green above, glaucous beneath, strongly reticulated, stipules 

 none : aments $ to 1 inch long on slender peduncles at the ends of the short 

 branches, opposite to the last leaf : scales obovate, purplish or yellow : capsule 

 ovate, tomentose, sessile, nectary " a laciniate cup surrounding the base of the 

 capsule " : style very short or none ; stigmas 2-cleft, brown, spreading. A 

 dwarf shrub of high alpine regions, with tortuous, buried stems, the leafy 

 tips and flowers rising a few inches above the surface. Rocky Mountains 

 and northward to the Arctic coast. Our plant is smaller than the European 

 type, with narrower and thinner leaves, less wrinkled above and fewer-flowered 

 aments. Extreme forms, in which the leaves are scarcely more than 2 to 3 

 lines in length and the aments reduced to 5 to 7 flowers, are designated var. 

 nivalis, Hook. sp. 



2. POPULUS, Tourn. POPLAR. COTTONWOOD. ASPEN. 



Trees with broad and more or less heart-shaped or ovate-toothed leaves, 

 and mostly angular branches : buds scaly, covered with a resinous varnish : 

 catkins long and drooping, appearing before the leaves. 



1. P. tremuloides, Michx. Tree 20 to 50 feet high, with smooth green- 

 ish-white bark; branches not angled : leaves roundish-heart-shaped, with a short 

 sharp point, and small somewhat regular leeth, smooth on both sides, with downy 

 margins : scales cut into 3 to 4 deep linear divisions, fringed with long hairs. 

 From California eastward across the continent, and northward to the Arctic 

 Ocean ; in the Rocky Mountains as far south as New Mexico. The " Quak- 

 ing Asp." The petiole is long, slender, and laterally compressed. 



2. P. aUglllata, Ait. A large tree, 80 feet high or upward ; branches 

 acutely angular or winged: leaves broadly deltoid or heart-ovate, smooth, crenate- 

 serrate, or with obtuse cartilaginous teeth. Extending from the Atlantic 

 States into our northeastern border, and abundant along the Platte. " Cot- 

 ton wood." 



3. P. balsamifera, L., var. candicans, Gray. A tall tree ; branches 

 round: leaves more or less heart-shaped, pointed, serrate, whitish and reticulate- 

 veined beneath ; petioles commonly hairy : scales dilated, slightly hairy : the 

 large buds varnished with copious fragrant resinous matter. From Colo- 

 rado northward and eastward to Lake Superior and New England. Com- 

 monly called " Cottonwood." 



4. P. angUStifolia, James. Branches terete, glabrous: leaves ovate- 

 lanceolate, attenuate at base, acute, glabrous, crenate-serrate. P. balsamifera, 

 var. angustifolia, Watson. From New Mexico and Colorado to California 

 and Washington Territory. 



