6io 



BETULACEAE. 



VOL. I. 



6. Betula alleghanensis Britton. Southern 

 Yellow Birch. Fig. 1499. 



B. alleghanensis Britton, Bull. Torr. Club 31 : 166. 1904. 



Similar to Betula lenta and to Betula lutea, the hark 

 either close and fissured, or peeling off in thin layers 

 on young trunks and branches. Leaves ovate or ovate- 

 oblong, usually acuminate at the apex, cordate or 

 rounded at the base, 5' long or less, sharply and rather 

 coarsely toothed, hairy when young, glabrous when old, 

 except on the veins beneath ; . staminate aments clustered ; 

 ripe pistillate aments oblong-cylindric, short-stalked or 

 sessile, about i' long, their bracts nearly or quite as 

 wide as long, more or less pubescent, 3-lobed to about 

 the middle, the margins ciliate; nut narrowly oblong to 

 obovate, broader than its wings. 



Woodlands, Massachusetts to Quebec, Michigan and 

 Georgia. May. 



7. Betula lutea Michx. f. Yellow Birch. Gray Birch. Fig. 1500. 



Betula lutea Michx. f. Arb. Am. 2: 152. pi. 5. 1812. 



A large forest tree, reaching a maximum height of 

 about 100 and a trunk diameter of 4, the bark yel- 

 lowish or gray, separating in thin layers or close, the 

 twigs gray-brown. Leaves ovate or oblong-ovate, mostly 

 acuminate at the apex, rounded, obtuse or rarely sub- 

 cordate at the base, sharply serrulate all around, dark 

 green and dull above, pubescent on the veins beneath, 

 1 3 '-4' long, petioles 4"-o," long; staminate aments usu- 

 ally 2-4 together; pistillate aments sessile, oblong or 

 oblong-cylindric, ij' or less long, 7 "-9" thick in fruit, 

 rather loose; bracts nearly equally 3-lobed to somewhat 

 above the middle, ciliolate, the lateral lobes ascending; 

 nut broadly oblong, wider than its wings. 



Newfoundland to Manitoba, Massachusetts, Pennsylvania 

 and Wisconsin. Wood hard, strong, light brown ; weight per 

 cubic foot 41 Ibs. Swamp- or silver-birch. April-May. 



8. Betula fontinalis Sargent. 



Western Red Birch. Cherry Birch. Fig. 1501. 



B. fontinalis Sargent, Bot. Gaz. 31 : 239. 1901. 



A shrub or rarely a tree attaining a height of 

 about 40 and a trunk diameter of il, the bark 

 smooth, dark bronze, the twigs gray-brown, warty. 

 Leaves broadly ovate or nearly orbicular, acute or 

 obtuse at the apex, sharply serrate, rounded or ob- 

 tuse at the base, short-petioled, glabrous on both 

 sides or sparingly pubescent on the veins beneath, 

 i '-2' long; petioles slender, 2 "-6" long; pistillate 

 aments peduncled, cylindric, spreading or pendent, 

 i'-ii' long, about 5" in diameter in fruit; fruiting 

 bracts ciliolate, about 3" long, their lateral lobes 

 ascending; nut much narrower than its wings. 



South Dakota to western Nebraska, British Columbia, 

 California and New Mexico, and on Mt. Albert, Quebec. 

 Has been confused with Betula occidcntalis Hook., and 

 referred to the Asiatic B. microphylla Bunge. Black, 

 gray, sweet or water-birch. April-May. 



