25^ 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 cylindric, 2 to 

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



The tree may be only a form of Betvia papyrifera 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 — Betnla ocddentalis 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, sharply and rather 

 coarsely toothed, commonly doubly toothed, 

 pointed, thin, 10 cm. long or less, usually 

 roimded 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 

 Fig. 208. — Western Birch. ygjjjg 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. 



7. KENAI BIRCH — Betnla 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 yoimg trees and on the branches of old ones; the young twigs are 



