FOREST TREES OF THE PACIFIC SLOPE. 263 



ALNUS. ALDERS. 



Trees and Shrubs of this group are known always as alders. The trees 

 an- of small or medium si/.c — rarely over 75 to '.»" feel in height. The hark is 

 often smooth and gray, sometimes marked conspicuously with large, chalky- 

 white areas; only the trunks of large trees have scaly hark — chiefly at the base. 

 The dense, brittle wood is composed largely of sapwood, with only a small core 

 of reddish brown heartwood. 



Alders shed their leaves in antnmn, but while they are still green. The 

 'eaves are conspicuously straight-veined, the veins from the midvein running to 

 tht margin of the leal*. Alder hnds, formed early in summer, are peculiar in 

 being raised on a well-defined, minute stem and in not being scaly. Male and 

 female flower clusters, each borne on different parts of the same branch, are 

 produced in a partly developed state the summer before they open. Botb are 

 then small, cylindrical bodies. The male clusters (the larger) become in sprint.' 

 from _ to <; inches long; they are pendent, and terminate a branchlet. Lower 

 down on the twig are produced the very much smaller female flower clusters, 

 which develop into small, woody, persistent cones, between the scales of which 

 numerous very small, flat seeds (nuts) are borne. The cones are green in 

 autumn when the seeds are mature, but later become brown, and in late fall or 

 in early spring they gradually open their scales and liberate the seeds. The 

 seeds of some species have very small and narrow gauze-like marginal wings, 

 while those of others are wingless ( liirs. 115 to 120). Seeds of the latter type 

 are rather heavy and are not distributed by the wind, hut depend for distribu- 

 tion largely upon water. Winged seeds are very buoyant and easily wafted by 

 the wind. 



Commercially the alders are of scarcely more than secondary importance. 

 Only one of the Pacific species produces useful wood; the others are too small 

 for any purpose except fuel, for which all species are very commonly used. 

 They grOw in moist or wet situations, from sea-level to over 7,000 feet elevation. 

 A common habitat is in river and canyon bottoms, along mountain streams, and 

 on wet mountain slopes. 



Six tree alders inhabit the United States and adjacent territory (on both the 

 north and south), while four of these occur within the Pacific region. Many 

 species of alders existed in the early epochs of the earth's history; remains of 

 them are found iu Eocene and Miocene rocks of the Tertiary period. 



White Alder. 



Mini* rhombifolia Nuttall. 



DISTINGUISHING <II VRACTERISTICS. 



The name "white alder" is not known to he used in the range of this tree, 

 but it is proposed for the want of a distinct common name, ami refers to the 

 tree's pale greenish foliage. So far as is now known, the tree's held name is 

 simply " alder."' 



Similar in general appearance to the red alder, from which it is probably 

 not distinguished by laymen. It differs from the latter tree in having thin. 

 conspicuously scaly, brown hark: the scaly bark extends considerably higher 

 up on the stem than that of red alder, which is commonly unbroken and smooth. 

 The stems are usually straight, from 50 to 75 feet high ami from is to - 1 

 inches in diameter, often only 30 or 40 feet high ami from 8 to 12 inches in 

 diameter. Trunks are clear of branches lor about one-half to two-thirds of 

 their length, and the civwu is rather broad, open, and dome-like, with middle 



