252 



The Birches 



are broadly ovate, rather long-pointed, heart-shaped at the base, 5 to 9 cm. long, 

 sharply toothed, the upper surface dark green and smooth, the lower pale green 

 and hairy in the axils of the veins. The ripe pistillate catkins are cyhndric, 2 to 

 4 cm. long, their scales smooth; the oblong nut is narrower than its wings. 



The tree may be only a form of Betula papyrijera Marshall, with heart-shaped 

 leaves, and it has been considered as a variety of that species. On mountain sum- 

 mits in New England and New York it is reduced to a mere shrub not over one 

 meter high. 



6. WESTERN BIRCH Betula occidentaUs Hooker 



This is the largest American birch, and one of the largest of all deciduous- 

 leaved trees, attaining a maximum height of about 40 meters, with a trunk diameter 



of a meter or more. It occurs in British Co- 

 lumbia and Washington, extending eastward 

 to Montana, inhabiting moist soil. 



The outer bark is yellowish brown and 

 shining, peeling off readily; the inner bark is 

 bright orange-yellow. The young twigs are 

 brownish, loosely hairy with long hairs, glan- 

 dular, becoming smooth, orange-brown and 

 shining. The pointed buds are about 6 mm. 

 long. The leaves are ovate, she rply and rather 

 coarsely toothed, commonly dovbly toothed, 

 pointed, thin, 10 cm. long or 'ess, usually 

 rounded or somewhat heart-shaped at the 

 base, glandular, and furnished with long 

 whitish hairs along the veins when young, 

 and with tufts of hairs in the axils of the 

 veins beneath when old; the stout leaf-stalks 

 are i to 2 cm. long; the stipules are oblong and about 2 cm. long. The tree 

 flowers in May. The staminate catkins are 7 to 10 cm. long, their scales hairy- 

 fringed. The ripe pistillate catkins are oblong-cylindric, 3 to 4 cm. long, stalked, 

 their finely hairy scales fringed on the edges, the middle lobe narrower and some- 

 what longer than the lateral ones; the nut is oval and narrower than its wings. 



Fig. 208. Western Birch. 



7. KENAI BIRCH Betula kenaica Evans 



This tree, named from specimens collected on the Kenai peninsula, inhabits 

 only the coast of Alaska; it is there known also as Red birch and Black birch; 

 it attains a height of about 13 meters, with a trunk up to 5 dm. thick. 



The thin bark peels off readily in layers; it is dark brown on large trunks, grayish 

 or reddish on young trees and on the branches of old ones; the young twigs are 



