BETULACE^ 195 



and dark chestnut-browu and lustrous above; staminate flowers composed of a mem- 

 brauaceous 4:-lobed calyx often 2-lobed by suppression, the anterior lobe obovate, 

 rounded at the apex, as long as the stamens, much longer than the minute posterior 

 lobe, and of 2 stamens inserted on the base of the calyx, with short 2-branched 

 filaments, each branch bearing an erect half-anther; pistillate aments oblong or 

 cylindrical, terminal on the short spur-like lateral branchlets, their scales closely 

 imbricated, oblong-ovate, 3-lobed, light yellow, often tinged with red above the 

 middle, accrescent, becoming brown and woody at maturity, and forming sessile or 

 stalked erect or pendulous short or elongated strobiles usually ripening in the 

 autumn, deciduous with the nuts from the slender rachis; calyx of the pistillate 

 flower 0; ovary sessile, compressed, with styles stigmatic at the apex. Nut minute, 

 oval or obovate, compressed, bearing at the apex the persistent stigmas, marked at 

 the base by a small pale scar, the outer coat of the shell produced into a marginal 

 wing interrupted at the apex. 



Betula is widely distributed from the Arctic Circle to Texas in the New World, 

 and to southern Europe, the Himalayas, China, and Japan in the Old World, some 

 species forming great forests at the north, or covering high mountain slopes. Of the 

 twenty-eight or thirty species now recognized thirteen are found in North America; 

 of these ten are trees. Of exotic species the European and Asiatic Betula alba, L., 

 in a number of forms is a common ornamental tree in the northern states, where 

 several of the Birch-trees of eastern Asia also flourish. Many of the species produce 

 wood valued by the cabinet-maker, or used in the manufacture of spools, shoe-lasts, 

 and other small articles. The thin layers of the bark are impervious to water and 

 are used to cover buildings, and for shoes, canoes, and boxes. The sweet sap pro- 

 vides an agreeable beverage. 



Betula is the classical name of the Birch-tree. 



CONSPECTUS OF THE NORTH AMERICAN ARBORESCENT SPECIES. 



Strobiles oblong'-ovoid, nearly sessile, erect, the lateral lobes of their scales broad and 

 slightly divergent ; wing not broader than the nut ; leaves with 9-11 pairs of veins; bark 

 of young branches aromatic. 



Leaves heart-shaped or rounded at the base ; scales of the strobiles glabrous ; bark 

 dark brown, not separating into thin layers. 1. B. lenta (A, C). 



Leaves wedge-shaped or slightly heart-shaped at the base ; scales of the strobiles 

 pubescent ; bark yellow or silvery white, separating into thin layers. 



2. B. lutea (A). 

 Strobiles oblong or cylindrical, erect, spreading or pendant, on slender peduncles ; wing 

 broader than the nut ; leaves with 5-9 pairs of veins. 



Strobiles oblong, erect, ripening in May or June, their scales pubescent, deeply lobed, 

 the lateral lobes erect. 



Leaves rhombic-ovate, glaucescent and more or less silky-pubescent beneath; bark 

 light reddish brown, separating freely into thin persistent scales. 



3. B. nigra (A, C). 

 Strobiles cylindrical, pendant or spreading. 



Scales of the strobiles pubescent, with recurved lateral lobes, the middle lobe trian- 

 gular, nearly as broad as long ; leaves long-pointed, their petioles slender, elon- 

 gated. 



Leaves triangular to rlioniboidal, bright green and lustrous ; bark chalky white, 

 not separable into thin layers. 4. B. populifolia (A). 



