0.84] 



CLASSIFICATION AND DESCRIPTION 



147 



6. B6tula nlgra, L. (RIVER OR RED 

 BIRCH.) Leaves 2i- 2 to 3i in. long, 

 rhombic-ovate, acute at both ends, dis- 

 tinctly doubly serrate, bright green 

 above ; glaucous beneath when young ; 

 on petioles only ^ their length. Twigs 

 brown to cinnamon-color, and downy 

 when young. A medium-sized tree, 

 30 to 50 ft. high, usually growing on 

 the edges of streams, the old trunks 

 having a very shaggy, loose, torn, red- 

 dish-brown bark. Wild in Massachu- 

 setts, south and west ; often cultivated. 



GENUS 84. ALNTJS. 



B. nlgra. 



Shrubs or small trees with deciduous, alternate, simple, 

 straight-veined leaves with large stipules that remain 

 most of the season. Flowers in catkins. Fruit a small, 

 scaly, open, woody cone, remaining on the plant through- 

 out the year. 



Native species ; growing in wet places. (A. ) 



A. Leaves rounded at base ; whitened beneath ; found north of 



41 N. Lat 1. 



A. Leaves acute or tapering at base; southward. (B.) 



B. Flowering in the spring 2. 



B. Flowering in the autumn 3. 



Cultivated species; from Europe; will grow in dry places . .4, 5. 



1. Alnus incana, Willd. (SPECKLED 

 OR HOARY ALDER.) Leaves 3 to 5 in. 

 long, broadly oval or ovate, rounded at 

 base, sharply serrate, often coarsely 

 toothed, whitened and mostly downy 

 beneath; stipules lanceolate and soon 

 falling. Fruit orbicular or nearly so. 

 A shrub or small tree, 8 to 20 ft. high, 

 with the bark of the trunk a polished 

 reddish greeii ; common along water- 

 courses north of 41 N. Lat.; sometimes 

 cultivated. 



