GENUS 4. 



BIRCH FAMILY. 



609 



3. Betula papyrifera Marsh. Paper or Canoe Birch. Fig. 1496. 



Betula papyrifera Marsh. Arb. Am. 19. 1785. 

 Betula papyracca Ait. Hort. Kew. 3: 337. 1789. 

 Betula papyrifera minor Tuckerm. Am. Journ. Sci. 45: 31. 

 1843. 



A large forest tree with maximum height of about 

 80 and trunk diameter of 3, or on mountains re- 

 duced to a low shrub; bark, except of the young wood, 

 peeling in thin layers. Leaves ovate, acute or acumi- 

 nate, dentate and denticulate, subcordate, truncate or 

 obtuse at the base, dark green and glabrous above, 

 glandular and pubescent on the veins beneath, slender- 

 petioled, 1-2 '-4^' long, i'-3' wide; petioles i'-ij' long; 

 staminate aments 2'-^' long; pistillate aments cylindric, 

 slender-peduncled, \'-2 f long, i'-4' in diameter in fruit; 

 fruiting bracts 2" -3" long, puberulent or ciliate; nut 

 narrower than its wings. 



Newfoundland to Alaska, Pennsylvania, Michigan, Ne- 

 braska and Washington. Similar to the Old World B. alba 

 L. Wood hard, strong, reddish-brown ; weight per cubic 



foot 37 Ibs. The chalky-white outer bark interesting to Y~ ^^^=-0, VxS. 2 



tourists. Silver-, bolean- or white-birch. Spool-wood. 

 April-May. 



Betula cordifolia Regel, differs in having distinctly cor- 

 date leaves, but scarcely otherwise. 



4. Betula nigra L. River Birch. Red Birch. 

 Fig. 1497. 



Betula nigra L. Sp. PI. 982. 1753. 



A slender tree, sometimes 90 high and the trunk 

 22 in diameter; bark reddish or greenish-brown, 

 peeling in very thin layers; twigs reddish. Young 

 shoots, petioles and lower surfaces of the leaves to- 

 mentose; leaves rhombic-ovate, apex acute or obtuse, 

 irregularly serrate or somewhat lobed, base cuneate, 

 when mature dark green and glabrous above, pale 

 and glabrous or somewhat tomentose beneath, li'-3' 

 long; petioles 3"-8" long; staminate aments mostly 

 clustered in 2 ! s or 3's, 2^-3^' long; pistillate aments 

 oblong-cylindric, spreading, peduncled, i'-2 r long, 

 5"-6" in diameter in fruit; fruiting bracts tomen- 

 tose, about equally 3-lobed, 3" -5" long; nut broadly 

 obovate, wider than its wings, pubescent at the base. 



Along streams and lakes, Massachusetts to Illinois, 

 Minnesota, Kansas, Florida and Texas. Wood hard, 

 strong, brown ; weight per cubic foot 36 Ibs. The bark 

 of the branches peels off in almost membranous layers. 

 Water- or black-birch. April-May. 



5. Betula lenta L. Cherry, Black or Sweet Birch. Fig. 1498. 



Betula lenta L. Sp. PI. 983. 1753. 



A large forest tree, sometimes 80 high, with dark 

 brown close smooth bark, becoming furrowed, not 

 separating in layers; foliage aromatic; twigs smooth, 

 warty, young leaves silky. Mature leaves ovate or 

 ovate-oblong, acute or acuminate, the base cordate 

 or_ rounded, sharply serrulate, bright green, and 

 shining above, dull green and pubescent on the veins 

 beneath, 2^-4' long, i'-2 r wide; petioles 3"-6" long; 

 staminate aments clustered, 2* '-4' 'long; pistillate 

 aments sessile, dense, oblong, about i' long and \' 

 in diameter in fruit, nearly erect; bracts glabrous or 

 minutely puberulent, not ciliate, appressed, about 2" 

 long, nearly equally 3-lobed, the lateral lobes some- 

 what divergent ; nut oblong, broader than its wings. 



New England to western Ontario, Florida and Ten- 

 nessee. Wood hard, strong, dark brown ; weight per 

 cubic foot 47 Ibs. The aromatic oil of the branches and 

 foliage (same as oil of wintergreen) is distilled in 

 quantities and is an important article of commerce. 

 Tree much resembles the cherry. A hybrid with fl. 

 pumila is B. Jackii Schneider. Spice-, river- or ma- 

 hogany-birch. Mountain-mahogany. April-May. 



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