G. 83) CLASSIFICATION AND DESCRIPTION 145 
* Trunks with chalky white bark. (A.) 
A. Native. (B.) 
B. Small tree with leafstalks about 14 as long as the blades. i. 
B. Large tree; leafstalks about 14 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. 4. 
C. Leaves not very aromatic; bark brownish and loose and 
shaggy on the main trunk; growing in or near the water. .6 
1. Bétula populifolia, Ait. (AmERI- 
CAN WHITE OR GRAY Brrou.) 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. populifolia. 
spaces below the branches; recent shoots brown, closely covered 
with round dots. 
2. Bétula papyrifera, Marsh. (PAPER OR CANOE Bircu.) 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 14 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, & 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 Eng 
land and westward, also cultivated. 
B. papyrifera. 
