1921] Smiley: Flora of the Sierra Nevada of California 153 



2. POPULUS 



Leaves orbicular with abrupt tip; petioles compressed; stamens few (6-12); 



small shrub or tree 1. P. tremuloides 



Leaves ovate or lanceolate, somewhat cordate at base; petioles not compressed; 



stamens numerous (40-60); large tree 2. P. trichocarpa 



1. Populus tremuloides Michx., Fl. Bor. Am., vol. 2, p. 243. 1803. 



Type locality. — "Hab. in Canada et Noveboraco. " 



Range. — Subarctic America south to California. New Mexico, 

 Missouri, and the Middle States. 



Zone. — Transition and Canadian. 



Specimens examined. — Webber Lake, Sierra County, Dudley, 

 June, 1900; Glen Alpine, Tahoe, 6,800 feet, McGregor 202; Carson 

 Spur, Alpine County, 8,500 feet, Hansen 197 ; Angora Peak, forming 

 chaparral along the east side, 7,800 feet. Smiley 18 ; Tenaya Lake, 

 Yosemite, 8,100 feet. Smiley 692 ; Lake of Islands, near Kaweah 

 Peaks, Tulare County, 11,000 feet, Dudley, August 31, 1894. 



The aspen is a very common member of the high mountain chap- 

 arral and in the Sierra does not seem to form the groves of tall slender 

 trees that are so conspicuous in many parts of the Colorado mountains. 



2. Populus trichocarpa T. and G., in Hook., Ic. PL, vol. 9, p. 878. 



1852. 



Type locality. — "Santa Clara River, near Beneventano (Ventura), 

 California. ' ' 



Range. — British Columbia to northwest Montana, south to south- 

 ern California. 



Zone.- — From the Upper Sonoran into the Canadian. 



Specimens examined. — Donner Lake, Dudley, June 14, 1900 ; be- 

 tween Fallen Leaf and Glen Alpine, Tahoe, 6,800 feet. Smiley 207; 

 Carson Spur, Alpine County, 8,500 feet, Hansen 803; South Fork 

 of the San Joaquin, 6,700 feet, Hall and Chandler 727. 



At the higher levels the characters of this tree vary somewhat 

 from the typical, the foliage becomes whiter, the leaf -form changes to 

 a longer and narrower type of leaf, while the cordate base is com- 

 pletely lost, the leaf -base being truncate or even ovate. 



