226 FOREST TREES OF THE PACIFIC SLOPE. 



the year are rather slender, but stiff in appearance, shiny yellow, later becoming 

 greenish. Mature leaves (fig. 93), from If to 3i inches long, are deep yellow- 

 green (paler beneath), smooth on both surfaces; the somewhat scythe-shaped 

 form of the leaves is a notable character. Midveins and stems of the leaves 

 are yellow. Wood, reddish brown, light, soft, and brittle. 



Longevity. — Not fully determined. Stems from 3 to 5 inches through are 

 from 13 to 22 years old. 



Great Slave Lake and southward (through region along eastern base of Rocky Moun- 

 tains) to northern Idaho and California (Lake County). 



OCCURRENCE. 



Borders of mountain streams in rocky and gravelly soil. Climatic and other require- 

 ments undetermined. 



White Willow. 

 Salix lasiolepis a Bentham. 



DISTINGUISHING CHARACTERISTICS. 



The white willow, so called on account of the smooth ashy gray bark (with 

 brownish tinge) of young trunks and limbs of older trees, varies in size from a 

 cluster of low shoots (at high elevations) to a tree from 15 to 25 feet in height 

 (at low elevations) with a diameter of from G to 10 inches. Very exceptionally 

 it is from 30 to 40 feet high and a foot or more in diameter. The slim branches 

 trend upward strongly in a rather narrow, irregular open crown. Bark of 

 larger trunks is less than one-half an inch thick, shallowly seamed, the wide 

 ridges connected here and there by smaller lateral ridges ; indistinctly dark 

 brown or blackish with occasional grayish areas oh the flat ridges. Mature 

 twigs of the season, rather thick, bear numerous leaves and are deep red-brown, 

 tinged with yellow toward their extremities, where they are very minutely 

 downy, but smooth lower down. Mature leaves (fig. 94), from 2* to about 5$ 

 inches long, are somewhat thick and leathery, with yellow stems and midveins, 

 dark yellow-green and smooth on their top sides, conspicuously silver-white 

 beneath, where the midveins and terminal leaves are minutely hairy. Wood : 

 Very little of the pale brown heartwood is formed, the main bulk of the trunk 

 being sapwood. Not used commercially, but in the southern range at a low 

 altitude, where fuel timber is scarce, it is locally used for fuel. 



Longevity. — Not fully determined. Stems from 5 to 9 inches in diameter 

 are from 12 to 22 years old. 



Northern California (Klamath River) and southward through the western part of the 

 State to Lower California and southern Arizona (Tanners Canyon on Iluachuca Moun- 

 tains, and White River Canyon on Chiricahua Mountains). 



° There is doubt, which can not be cleared up at present, as to whether this name is 

 older than Salur bigelovii Torrey, supposed to have been published in 1856 or January, 

 1857, while 8. lasiolepis Bentham appeared in February, 1857. Torrey, however, cites 

 other species of Salix described and published by Bentham with his S. lasiolepis, and 

 this seems to show conclusively that the latter's name was actually published before 

 Torrey's S. bigelovii, notwithstanding the printed earlier date of the document containing 

 Torrey's name of this willow. 



