(337) 
Specimens examined: Elizabeth Lake, Liebre Mountains, 4)- 
rams €F McGregor 412; Rock Creek, San Gabriel Mountains, 
Abrams &§ McGregor 556; near Claremont, Baker 5347; Cajon 
Pass, Abrams &F McGregor 695; San Bernardino, Parish, March, 
1902; San Dieguito River, near San Dieguito (Bernardo), Abrams 
3370; Calexico, G. D. Abrams, Feb., 1910. 
3. PopuLus TREMULOIDES Michx. Fl. Bor. Am. 2: 243. 1803. 
Type locality: ‘““Hab. in Canada et Noveboraco.” 
Distribution: The quaking aspen is distributed through the 
Canadian Zone of California, and extends from San Pedro Martir 
northward to Alaska, thence across the northern part of the con- 
tinent, ranging southward along the mountains to New Mexico 
and Pennsylvania. Only one locality has been discovered in 
southern California, viz., Grinnell (Univ. Calif. Pub. Zoology 5: 34. 
1908) reports several groves ‘fon the west side of the upper 
Fish Creek Canyon, north of San Gorgonio Peak, at altitudes of 
7000 to 7600 feet.” 
2. SALIX. Wittow. 
Stamens 3 or more; bark furrowed; trees. 
Leaves green on both surfaces; stipules glandular; ovary often pubescent. 
1. S. vallicola. 
Leaves pale beneath; capsule glabrous. 
Petioles with glands near the base of the blade; stipules conspicuous, 
glandular. 2. S. lasiandra. 
Petioles and stipules not glandular, the latter often wanting. 
3. S. laevigata. 
Stamens 2; bark not furrowed; trees or shrubs. 
Scales of the ament black or black-tipped. 
Ovary and capsule glabrous. 
Leaves entire or remotely and obscurely serrate, becoming rusty= 
glaucous beneath; scales pubescent or short-villous. 
4. S. lasiolepis. 
Leaves finely serrate, becoming smooth and pale beneath; scales 
long-villous. 5. S. Watsoni. 
Ovary and capsule pubescent. 
Aments appearing before the leaves; styles none. 
6. S. Scouleriana. 
Aments appearing with the leaves; styles evident. 
7. S. glaucops. 
Scales of the ament pale. 
Ovary glabrous; leaves sparsely appressed-pubescent. 
8. S. exigua. . 
Ovary pubescent at least sparsely so when young; leaves more or 
less densely silky. 9. S. argophylla. 
