BETULA 247 



A genus of about 40 species, natives of the arctic and north temperate 

 zone. 



Key to the Species 



1. Trees, with white bark 



a. Leaves serrate or toothed, not deeply cut 



( 1 ) Bark peeling in papery layers, leaves 



ovate, native B. papyri f era 



(2) Bark peeling slightly above, dark and 



furrowed at the base, leaves triangular B. verrucosa 



b. Leaves deeply cut 



( 1 ) Leaves with long slender points B. populifoHa 



laciniata 



(2) Leaves cut, but not very long-pointed B. verrucosa lobata 



2. Trees or shrubs with gray, yellow, or dark bark 



a. Trees 



( 1 ) Twigs fragrant, bark very ragged, yel- 



lowish gray B. lutea 



(2) Twigs not fragrant, bark reddish brown, 



trunk scaly B. nigra 



b. Shrubs 



( 1 ) Tall shrubs, 4-8 m. high, leaves ovate B. Sandbergii 



(2) Shrubs, 1-2 m. high, leaves obovate to 



orbicular B. pumila 



Betula papyrifera Marshall 1785 Paper Birch Canoe Birch 

 Betula alba var papyrifera (Marshall) Spach 



A large tree, reaching a maximum height of 25 m. (78 ft.), and a 

 trunk diameter of 2-5 dm.; bark white (except on young trees where it 

 is brownish red) and peeling off in papery layers, twigs slender with pale 

 lenticels ; leaves ovate, obtuse, truncate or sub-cordate at the base, acu- 

 minate at the apex, usually doubly and often irregularly serrate, dark 

 green and glabrous above, pubescent abong the veins beneath and glandu- 

 lar or resin-dotted, 5-8 cm. long, 3-5 cm. wide; staminate catkins 5-10 

 cm. long ; pistillate catkins slender, erect, at the ends of short leafy shoots 

 2-3 cm. long, fruiting catkin drooping, 3-5 cm. long, 7-10 mm. in di- 

 ameter, fruiting bracts about 4 mm. long puberulent, nut oval : papyri- 

 fera, paper bearing. 



Common and in places very abundant throughout the state except 

 southwestward. Distributed from Newfoundland and Labrador to Hud- 



