266 FOREST TREES OE THE PACIFIC SLOPE. 



somewhat lighter weight than that of the red alder. Its principal value is fot 

 fuel, hut it is suitable for cabinet work. 



Longevity. — Little is known of the age limits. Trees from 12 to 15 inches 

 in diameter are from 37 to 50 years old. 



RANGE. 



From northern Idaho to the eastern slope of the Cascade Mountains of Washington 

 and southeastern Oregon, and southward through California (coast ranges, western 

 slopes Sierra Nevada, San Bernardino, San Jacinto, and Cuyamaca mountains). 



OCCURRENCE. 



Canyon bottoms and borders of foothill and lower mountain streams, commonly in moist 

 gravelly or rocky soils. Forms dense stretches, lines, and patches of pure growth, and 

 is often mingled with California sycamore, Oregon ash, western dogwood, and, occa- 

 sionally broadleaf maple. 



Climatic Conditions. — Similar to those of Oregon ash. 



Tolerance. — Endures great deal of shade throughout life, but requires moderate over- 

 head light for best height growth ; dense side shade clears and produces long stems. 



Reproduction. — Abundant seeder in open stands on stream borders, where crowns are 

 large ; much less prolific in dense stands. Reproduction frequent and best in moist or 

 wet sand, gravel, or humous soil, where seedlings grow- rapidly. 



Mountain Alder. 



Alnus ten iii folia Nuttall. 



DISTINGUISHING CHARACTERISTICS. 



Mountain alder has no distinctive field name, but is called simply " alder." 

 The name mountain alder, here proposed, refers to the tree's high mountain 

 habitat. 



Very commonly with slender, bent stems, from G to 15 feet high (in dense 

 thickets), or, at best, 20 or 25 feet high, and under G inches in diameter (rarely 

 with a straight trunk). The narrow, dome-like crown of larger trees is com- 

 posed of slim branches which stand out and droop a little. On small trunks the 

 bark is smooth, thin, and dark gray-brown ; on larger trunks it is lightly seamed, 

 with thin scales, and brown tinged with red. Season's twigs, with clear red, 

 very minutely downy buds, are pale brown, tinged with purple-red, shading 

 into gray lower down. Mature leaves (fig. 117), about 2i to Hi inches long, or 

 4 to 44 inches long on strong shoots, are deep grass-green and smooth on their 

 upper surfaces ; beneath they are very light yellowish green, usually smooth, but 

 sometimes minutely downy ; leaf stems and midveins, yellow. Borders of leaves 

 cut into coarse teeth which are themselves finely and sharply toothed, the teeth 

 pointing forward. Mature cones, about one-half to five-eighths of an inch long; 

 ends of cone scales very thick and with about 4 minute rounded lobes, or sub- 

 divisions — ends sometimes without these and -squarish. Seeds with very nar- 

 row, very thin borders (fig. 117, a). Flowers open in early spring, when the male 

 clusters become 2 to 3 inches long and about three-sixteenths of an inch thick. 

 Wood, light brown. Of no commercial use on account of the small size of the 

 tree. 



Longevity. — Not fully determined. Stems from 2 to 5 inches in diameter 

 are from 14 to 37 years old. 



Important as a member of the forest on account of the protection it affords 

 the headwaters and lower courses of mountain streams and springy slopes. 



