123 Muhlenbergia, Volume 8 



bright green, thick, distinctly channeled above, ridged beneath, 

 with a channel on each side of the ridge, the apex commonly 

 blunt and rounded. 



Some two years ago when the question of identifying our 

 white fir came up, I was much confused by the varying descrip- 

 tions of A. concolor^ but finally decided that it must be that spe- 

 cies, but not agreeing altogether with any of the descriptions. 



In Sargent's Manual the leaves of A. concolor are described 

 as follows: "On lower branches flat, straight, rounded, acute or 

 acuminate at the apex. . on fertile branches and on old trees 

 frequently thick, keeled above, usually falcate, acute, or rarely 

 notched at the apex." 



Sud worth, in Forest Trees of the Pacific Slope ii6, says: 

 "Young foliage of the year is yellow-green, with a bluish cast, 

 but later it turns to a pale yellow-green, with a whitish tinge. 

 The leaves are flat, straight, and full and plump on the upper 

 side, blunt or pointed — usually not prickly, but sometimes 

 prickly on the lower crown branches of old trees. They stand 

 out distinctly from the two sides of the lower branches by the 

 twist in their bases; but very commonly the lower branches of 

 young trees have their leaves curved and standing erect, some- 

 what in two lines, from the upper sides of the twigs. Leaves of 

 the upper crown, especially on the topmost branches, are strongly 

 curved or sickle-shaped, and appear to grow from the upper 

 sides of the branchlets. These leaves and those on leaders are 

 sharp-pointed. Lower branch leaves are usually longer (i and 

 a third to 3 inches long) than those of the upper branches, which 

 are commonly about i to i and a third inches long. There is 

 very great variation in the length, form, and thickness of leaves 

 of this fir in different parts of its wide range. The changes in 

 form from horizontally flattened leaves to vertically flattened 

 ones, or to those resembling a sickle-blade, are curious; they are 

 unexplained, except perhaps by the fact that the latter form is 

 best adapted to the dry climate in which it most often occurs. 

 Some authors hold that Rocky Mountain trees bear longer 

 leaves, and more commonly pointed ones, tiian do trees of the 

 Pacific forests. The writer has seen trees '\\\ the latter region 



