256 FOEEST TREES OF THE PACIFIC SLOPE. 



Not locally called " western birch," but simply " birch." It is very desirable, 

 however, to use the mure distinctive name given here, which is derived from the 

 tree's technical name. 



It is the largest of our birches and, indeed, of any known species of birch. 

 Height, from 80 to 90 feet (not rarely 100) ; diameter, from 2 to 3 feet, or 

 occasionally larger. The smooth, shiny, light orange-brown trunks are clear 

 of branches for from 40 to GO feet, while the branches of the spreading, open, 

 round-topped crown droop considerably. Young trees have rather compact, 

 conical-shaped heads. All but the lower slender branches trend upward, but 

 with age they become more and more drooping. The thin bark is separable 

 into thin sheets, the freshly exposed surface being a clear orange-color. Year- 

 old twigs are clear, light yellowish-brown, more or less very minutely hairy, 

 and with very few speck-like glands (abundant on young twigs) ; later, the 

 twigs become smooth and are without hairs and very shiny. Mature leaves 

 (fig. Ill), from 2| to 34 inches long, are thin, marked with minute dots (made 

 by resinous glands which cover the young leaves), dull deep green above (mid- 

 veins hairy) and light yellowish green beneath, where the yellow midvein and 

 its larger branches are minutely hairy. Leaf stems, more or less hairy and 

 minutely glandular. Mature cones (fig. Ill), somewhat erect, are about 1§ to 

 1J inches long and one-half inch or slightly less in diameter. Cone-scales 

 (fig. Ill, b) very minutely hairy on the outside, especially on the margins. 

 Minute seeds (nuts) with pale, very thin wings on two sides (fig. Ill, c). 

 Wood : Nothing now known of the characteristics of the wood, but since the tree 

 occurs only occasionally, it is not likely to be commercially important. 



Longevity. — No records of age are available. 



RANGE. 



Extreme northwestern Washington and southwestern British Columbia : possibly in 

 central British Columbia, eastern Washington, Idaho, and Montana. Range little known 

 at present. 



British Columbia. — Mainly in Lower Fraser River Valley; a few trees at various 

 points on Vancouver Island, and reported at Donald, on Columbia River (long. 118°). 



Washington. — Vicinity of Puget Sound, extending inland on Skagit River (above 

 Ruby Creek) to 4,000 feet in Cascades, and southward at least to Seattle ; occurs also 

 on islands of Puget Sound and on shores of Gulf of Georgia and Straits of Fuca. Lo- 

 cally noted at Sumas Prairie and Everson. in Whatcom County. Reported on Tukannon 

 River in eastern Washington, in Blue Mountains, at a point 10 miles southwest of Pull- 

 man, and in Whitman and Stevens counties. Much more careful field study is required to 

 define the eastern range of this tree, which appears to approach, in some individuals, 

 occasional western forms of Betula papyrifera. A birch recently found in Idaho and 

 Montana resembles the latter species, but it is suspected of being B. occidentalis. 



OCCURRENCE. 



On borders of streams, margins of meadows and lakes, in rich, moist, humous sandy and 

 rocky soils. Nothing further known now of occurrence nor of silvical characteristics. 



Kenai Birch. 

 Betula kenaica Evans. 



DISTINGUISHING CHARACTERISTICS. 



The Kenai birch is a comparatively new and little known Alaskan birch, 

 called "red birch'' and "black birch," names long used for the eastern birch 

 (Betula nigra). The name "Kenai birch." coined from the technical name, is 

 proposed to avoid confusion with names already appropriated. 



