250 



The Birches 



It is reported to grow to a height of about 26 meters, with a trunk 3 or 4 dm. thick, 



but it is usually much smaller. It inhabits mountain sides and river banks. 



The bark of the trunk is white or whitish, that of the branches pale reddish 



brown. When young the twigs are densely 



resinous-glandular, becoming smooth and 



red-brown. The buds are ovoid, blunt, 



about 6 mm. long, their scales sometimes 



fringed with white hairs. The leaves are 



triangular-ovate, sharp-pointed, irregularly 



sharply toothed, 4 to 8 cm. long, and usually 



nearly as wide as long, firm in texture, 



smooth when old, somewhat hairy when 



young; they are dark green and dull on the 



upper surface, hght green on the lower; the 



slender leaf-stalks are 1.5 to 3 cm. long, the 



stipules oblong. The staminate catkins are 



borne 2 or more together, and have ovate 



pointed scales. The ripe pistillate catkins 



are cylindric, about 3 cm. long, i to 1.3 cm. 



thick; their scales have hairy-fringed edges, 



the lateral lobes wider but scarcely longer 

 Fig. 205. — Alaska Birch. , . . , . , „ , . , 



than the pomted middle one; the nut is oval, 



about 2 mm. long, its wings rather broader than the body. 



It has been proposed to unite this species with the Betula pendula Roth, of 

 northern Europe and Asia, but the foliage of the two seems abimdantly distinct. 

 It has formerly been erroneously considered as identical with the Betula alba ver- 

 rucosa var. resinijera of northeastern Asia, and the name B. resinijera Britton 

 has been proposed for it. 



4. PAPER BIRCH — Betula papyrifera MarshaU 



m 



The Paper birch, or Canoe birch, grows mostly in forests, and ranges from 

 Newfoundland to Alaska, south to New Jersey, Pennsylvania, Michigan, Nebraska, 

 Colorado, and Washington, thus extending nearly or quite across the continent; 

 its leaf-form is somewhat variable, and it has been held by various authors as 

 identical with the White birch of Europe {Betula alba L.), but an examination of 

 the two trees growing side by side will at once demonstrate that, while similar, 

 they are different. It attains a maximum height of about 25 meters, with a trunk 

 diameter of about 7 dm. B. Andrewsii A. Nelson, is probably not distinct. 



The bark is usually bright white outside, orange or yellow within, quite thick, and 

 peels off readily in thin layers; at the bases of old trees it is often black and rather 

 deeply fissured, and there are often black bands higher up on the trunks. The 

 young green twigs are a little viscid and quite hairy; they become smooth and 



