BETULACEA. 
SILVA OF NORTH AMERICA. 
59 
BETULA ALASKANA. 
White Birch. 
STROBILES cylindrical, pendulous. Leaves rhomboidal to deltoid, ovate, acumi- 
nate. : 
Betula Alaskana, Sargent, Bot. Gazette, xxxi. 236 (April, 
ISOs 
Betula alba, subsp. verrucosa, var. resinifera, Regel, 
tula und Alnus) (in part) (1865); De Candolle Prodr. 
xvi. pt. ii. 164. ei 
Betula resinifera, Britton, Bull. N. Y. Bot. Gard. ii. 165 
Bull. Soc. Nat. Mosc. xxxviii. pt. ii. 398 (Gattungen Be- (not Regel) (May, 1901). 
A tree, usually from thirty to forty but occasionally eighty feet in height, with a trunk from six 
to twelve inches in diameter, and slender erect and spreading or pendulous branches. The bark of the 
trunk, which is thin and marked by numerous elongated horizontal dark and only slightly raised lenti- 
cels, is dull, pale reddish brown or sometimes nearly white on the outer surface, light red on the inner 
surface, close and firm, and finally separable into thin plate-like scales. The branchlets are slender, 
glabrous, bright red-brown, more or less thickly covered during their first year with resinous glands 
which do not always entirely disappear until the second or third season, when the branchlets are lustrous 
and marked by numerous small pale lenticels. The winter-buds are ovate, obtuse at the gradually nar- 
rowed apex, and about a quarter of an inch in length, with light red-brown and shining outer scales 
sometimes ciliate on the margins, with long white hairs, and oblong rounded scarious inner scales 
which are hardly more than half an inch long when fully grown. The leaves vary from rhomboidal to 
deltoid-ovate, and are acuminate and long-pointed at the apex, truncate, rounded or broadly cuneate or 
on leading shoots occasionally cordate at the entire base, and coarsely and often doubly glandular-serrate 
above; when they unfold they are yellow-green and covered with resinous glands, lustrous and villose 
above, with long scattered pale hairs, and slightly puberulous below; and at maturity they are thin, 
dark green on the upper surface, pale and yellow-green on the lower surface, from an inch and a half 
to three inches long and from an inch to an inch and a half wide, with slender midribs and primary 
veins pubescent or ultimately glabrous below, and slender often bright red petioles which are at first 
somewhat hairy but finally glabrous and about an inch in length. The stipules are oblong, gradually 
narrowed and rounded at the ends, and villose particularly toward the margins. The aments of 
staminate flowers are clustered, sessile, about an inch long, and an eighth of an inch thick, and their 
scales are ovate, acuminate, puberulous on the outer surface, and light red with yellow margins. The 
pistillate aments are slender, cylindrical, glandular, about an inch long and an eighth of an inch 
thick, and are raised on stout peduncles nearly half an inch in length. The strobiles are cylindrical, 
spreading, or pendulous, from an inch to an inch and a quarter long, and from one third to one half 
of an inch thick; and their scales are almost as long as they are broad and ciliate on the margins, 
with erect and acute or spreading and rounded lateral lobes, much shorter than the elongated acute or 
acuminate terminal lobe. The nut is oval and narrower than its broad wing.! 
Betula Alaskana is distributed from the valley of the Saskatchewan from about longitude 106° 
1 In 1858 B collected sp of this tree on the Sas- 
be unlike any of the Asiatic species, and with the scanty know- 
katchewan (teste Herb. Gray). These specimens were referred by 
Regel to one of his varieties of the Old World, Betula alba from 
Udskai in eastern Siberia and from Transbaical, but the Alaskan 
specimens which I have sent to the Imperial Botanic Garden at St. 
Petersburg are pronounced by the botanist of that establishment to 
ledge which now exists of many of the northern Asiatic Birches it 
does not seem possible to unite American and Asiatic forms until 
a thorough study of them can be made in the forest and the differ- 
ent species can be cultivated side by side. 
