G.83] 



CLASSIFICATION AND DESCRIPTION 



145 



* Trunks with chalky white bark. (A.) 

 A. Native. (B.) 



B. Small tree with leafstalks about j as long as the blades. 1. 



B. Large tree; leafstalks about ^ as long as the blades 2. 



A. Cultivated ; from Europe ; many varieties 3. 



* Bark not chalky white, usually dark. (C.) 

 C. Leaves and bark very aromatic. (D.) 



D. Bark of trunk yellowish and splitting into filmy layers. .5. 



D. Bark not splitting into filmy layers 4. 



C. Leaves not very aromatic ; bark brownish and loose and 

 shaggy on the main trunk; growing in or near the water. .6. 



1. B6tula populifolia, Ait. (AMERI- 

 CAN WHITE OR GRAY BIRCH.) Leaves tri- 

 angular, very taper-pointed, and usually 

 truncate or nearly so at the broad base, 

 irregularly twice-serrate; both sides 

 smooth and shining, when young glutin- 

 ous with resinous glands ; leafstalks half 

 as long as the blades and slender, so as 

 to make the leaves tremulous, like those 

 of the Aspen. Fruit brown, cylindrical, 

 more or less pendulous on slender pe- 

 duncles. A small (15 to 30 ft. high), 

 slender tree with an ascending rather 

 than an erect trunk. Bark chalky or 



grayish white, with triangular dusky B. popuiiToiia. 



spaces below the branches; recent shoots brown, closely covered 

 with round dots. 



2. B6tula papyrif era, Marsh. (PAPER OR CANOE BIRCH.) Leaves 

 2 to 4 in. long, ovate, taper-pointed, heart-shaped, abrupt or some- 

 times wedge-shaped at the base, sharply and doubly serrate, smooth 



and green above, roughly reticulated, glan- 

 dular-dotted and slightly hairy 'beneath ; 

 footstalk not over ^ the length of the blade. 

 Fruit long-stalked and drooping. A large 

 tree, 60 to 75 ft. high, with white bark 

 splitting freely into very thin, tough layers. 

 A variety, 5 to 10 ft. high (var. minor), oc- 

 curs only in the White Mountains. Young 

 shoots reddish or purplish olive-green deep- 

 ening to a dark copper bronze. New En 

 B a ifera. land and westward, also cultivated. 



