chalky white, not separable into thin layers. 4. B. populifolia (A). Leaves ovate, cuneate to truncate or rounded at base, dull blue-green; bark white tinged with pink, lustrous, not easily separable into thin layers. 5. B. cœrulea (A). Scales of the strobiles with ascending or spreading lateral lobes, the middle lobe usually acuminate, longer than broad; leaves acute or acuminate. Bark separating freely into thin layers; scales of the strobiles glabrous. Bark creamy white, or in some forms orange-brown; leaves ovate. 6. B. papyrifera (A, B, C, F). Bark dull reddish brown or nearly white; leaves rhombic to deltoid-ovate. 7. B. alaskana (A, B). Bark not separable into thin layers, dark brown; scales of the strobiles glabrous or puberulous; branchlets glandular. Leaves ovate, acute or acuminate, truncate or rounded at the broad base. 8. B. fontinalis (B, F, G). Leaves broad-ovate to elliptic, acute, rounded or abruptly short-pointed, cuneate at base. 9. B. Eastwoodæ (F). 1. Betula lenta L. Cherry Birch. Black Birch. [Illustration: Fig. 194] Leaves ovate to oblong-ovate, acute or acuminate, gradually narrowed and often unequal at the cordate or rounded base, sharply serrate with slender incurved teeth, or very rarely laciniately lobed (f. _laciniata_ Rehdr.), when they unfold light green, coated on the lower surface with long white silky hairs, and slightly hairy on the upper surface, at maturity thin and membranaceous, dark dull green above, light yellow-green below, with small tufts of white hairs in the axils of the veins, 2½′—6′ long, 1½′—3′ wide, with a yellow midrib and primary veins prominent and hairy on the lower surface, and obscure reticulate cross veinlets; turning bright clear yellow late in the autumn; petioles stout, hairy, deeply grooved on the upper side, ¾′—1′ long; stipules ovate, acute, light green or nearly white, scarious and ciliate above the middle. Flowers: staminate aments during the winter about ¾′ long, nearly ¼′ thick, with ovate acute apiculate scales bright red-brown above the middle and light brown below it, becoming 3′—4′ long; pistillate aments ½′—¾′ long, about ⅛′ thick, with ovate pale green scales rounded at the apex; styles light pink. Fruit: strobiles oblong-ovoid, sessile, erect, glabrous, 1′—1½′ long, about ½′ thick; nut obovoid, pointed at base, rounded at apex, about as broad as its wing.