Gray Birch 



247 



Leaves cuneate at the base, coarsely serrate. 

 Small trees or shrubs with serrate leaves. 

 Lateral lobes of the strobile-scales ascending or erect, shorter 



than the middle one. 

 Lateral lobes of the strobile-scales spreading, as long as the 

 middle one or a little longer. 

 Strobiles over i cm. thick; lateral lobes of their scales 



pointed. 

 Strobiles narrowly cylindric, less than i cm. thick; lateral 

 lobes of their scales rounded. 

 Leaves rhombic to rhombic-ovate, acute at both ends or broadly 

 cuneate at the base. 

 Leaves gray-tomentulose beneath; strobile-scales lobed at the 

 apex; nut ovate-orbicular, 3 to 4 mm. long, much wider than 

 its wings. 

 Leaves green and glandular beneath; strobile-scales lobed nearly 

 to the middle; nut 1.5 to 2 mm. long, about as wide as its 

 wings or narrower. 

 Fruiting catkins sessile or very short-stalked at the ends of short 

 branches; eastern trees. 

 Fruiting scales 4 to 5 mm. long; leaves mostly cordate. 

 Fruiting scales glabrous; bark dark brown, close. 

 Fruiting scales ciliate; bark rough or peeling, gray to yellow- 

 brown. 

 Fruiting scales 8 to 10 mm. long, hairy, ciliate; bark yellow-gray; 

 leaves rarely cordate. 



7. B. kenaica. 



8. B. joniinalis. 



9. B. utahensis. 



10. B. Piperi. 



11. B. nigra. 



12. B. Sandbergi. 



13. B. lenla. 



14. B. alleghanensis. 



15. B. lulea. 



I. GRAY BIRCH — Betula populifoUa Marshall 



A slender tree, usually growing in clusters in moist soil, along streams or 

 swamps, but also occurring on upland hillsides. 

 It extends from Prince Edward island to Dela- 

 ware, westward to western New York, eastern 

 Pennsylvania, and, according to a specimen 

 collected by Dr. Short, also to Kentucky; it is 

 most abundant near the coast. It attains a 

 maximum height of about 14 meters, with a 

 trunk diameter of 4 to 5 dm. When growing 

 along the borders of woods the trunk bends 

 away from the neighboring trees; it is very 

 flexible and is often bent to the ground by snow. 

 The tree is also known as American white birch, 

 and Old field birch. 



The outer bark is chalky white, the trunks 

 being thus very conspicuous in winter land- 

 scapes; it does not peel off readily; the inner ^'°- 202- — Gray Birch, 

 bark is orange-yellow and about 6 mm. thick on old trunks. The young twigs are 



