BETULA 



69 



pointed, divergent, mostly glabrous; 



twigs brown to black, quite aromatic 1. B. lenta 



b. Bark on old trunks bronze, scaly; buds 

 appressed, at least along the lower 

 half, often hairy; twigs greenish-brown, 

 somewhat aromatic 2. B. lute a 



a. Twigs without a wintergreen fragrance 



b. Bark on old trunks grayish- white, 

 usually close; twigs gray, with promi- 

 nent warty lenticels;buds short, taper- 

 ing both ways from the middle 4. B. populifolia 



b. Bark on old trunks exfoliating in thin 

 strips; twigs brown to black; buds 

 tapering from base to apex 



c. Twigs and buds somewhat hairy; 

 twigs reddish-brown;freshly ex- 

 posed bark on old trunks salmon- 

 pink or greenish-brown, the older 

 dark. 



c. Twigs and buds mostly glabrous; 

 twigs nearly black; bark on old 

 trunks chalky -white 



3. B. nigra 



5. B. papyrifera 



1. B^ lenta L. Sweet Birch. Black Birch. Cherry Birch . A 

 tree 15-20 m. high, 6-12 dm. in diameter; bark dark-brown,close,. 

 smooth, becoming furrowed, not separating in layers, the young 

 bark having a very sweet wintergreen taste; lenticels prominent; 

 twigs glabrous, slender and pliable, red-brown; fruiting catkins 

 short-cylindric, 1.5-3.5 cm. long, the scales firm and smooth; 

 nut oblong, with narrow wings. Rich woods, Maine to Ontario, 

 south to Georgia and Tennessee (Fig. 53 ). 



2. B, lutea Michx. f. Yellow Birch. A tree 20-30 m. high, 

 and 6-12 dm. in diameter; bark of trunk yellowish or silvery-gray, 

 detaching in thin filmy layers; twigs gray-brown, somewhat aromat- 

 ic; fruiting catkins oblong, 2-4 cm. Jong, the scales pubescent; 

 nut oblong, with narrow wings. Rich cool woods. Nova Scotia to 

 Ontario, south to North Carolina and Iowa (Fig. 54 ). 



3. B. nigra L. River Birch. Red Birch . A tree 15-30 m. 

 high, 3-9 dm. in diameter; bark reddish-brown, deeply furrowed 

 and broken into thin irregular scales, exposing the orange -red 

 close bark underneath; twigs reddish; buds hairy, the lower scales 

 elongated; fruiting catkins thick-cylindric, 2. 5-3. 5 cm. long, the 



