SALICINEiE. (WILLOW FAMILY.) 359 



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

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

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

 over which it spreads, making a dense mass 4 to 10 feet in dianjet4?r. Old 

 Marias Pass, Alontana, alt. 6 to 8,000 feet, Sargent d: Cauby. AIko in Canada 

 and Labrador. 



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

 rounded at base or mostly suhattcmiate iiito a long and slender prliuU, (luite 

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

 none : aments ^ to 1 inch long on slender peduncles at the ends of the hhort 

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

 ovate, tomentose, sessile, nectary, "a laciniate cupsurrotnnling 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 MounUina 

 and northward to the Arctic coast. Our plant is smaller than the Kur«-jK..an 

 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, Toura. Poplar, Cottonwood. Aspen. 



Trc^s 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, ]\lichx. 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 teeth, smooth on both sides, xcith doicny 

 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 *' (^'uak- 

 ing Asp." The petiole is long, slender, and laterally com])ressed. 



2. P. angulata, Ait. A large tree, 80 feet high or upward ; brnnchfs 

 acutely angular or icinged : leaves broadly deltoid or Iwart-ovate, smooth, cr-^nate- 

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

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

 tonwood." 



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

 round: leaves more or less heart-shaprd, pointed, serrate, ifhitish and reticulaU- 

 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 Enghuul. Com- 

 monly called "Cottonwood." 



4. P. angustifolia, James. Branches terete, glabrous: lenves otxiU- 

 lanceolate, attenuate at base, acute, glabrous, crcimlc-scrrate.—P. balsamifera, 

 var. angicstifolia, Watson. From New Mexico and Colonulo to Californin 

 and Washington. 



