SJ'i'A'ri': RoAiii) of FoHi'isTiiv. 155 



the apex^the persistent stigmas. Trees or shru})s, the l)ark and 

 wood of some of which contain an aromatic volatile oil. 



Bark of twigs frequently with a slight wintergreen flavor; 

 fruiting aments sessile or nearly so; leaves with 7-15, 

 usually 9-11 pairs of veins; wings of nut about as wide 



as the body 1 B. hitea. 



Bark of twigs usually bitter, not wintergreen flavored; 

 fruiting aments stalked; leaves with 5-9 pairs of veins; 

 wings of nut wider than the body. 

 Bark of trunk greenish-white to reddish-brown, scaly 

 and usually shaggy, leaves glaucous beneath; fruit- 

 ing aments erect or nearly so 2 B. nigra. 



Bark of trees chalky white, not scaly or shaggy; leaves 

 not glacous beneath; fruiting aments drooping or 

 spreading. 

 Upper surface of leaves shiny; staminate catkins usu- 

 ally solitary; dark triangular spots on the bark 



at the base of the limbs 3 B. populifoli:i. 



Upper surface of leaves not shiny; staminate catkins 

 usually 2 or 3; no dark spots on the bark at the 

 base of the limbs 4 B. pajiyrifera. 



1. Betula lutea Michaux. Birch. Plate 35. Bark of old 

 trunks fissured into wide plates, usually rolling back from one 

 edge, rarely tight, dull dark brown, bark of small trees and the 

 branches of old trees silver or dark gray, freely peeling off in thin 

 strips, never smooth; the year's shoots hairy, greenish gray, becom- 

 ing smooth and reddish-brown by the end of the second year, not 

 aromatic when bruised, sometimes when chewed a faint winter- 

 green odor may be detected; winter buds pointed, light to a reddish- 

 brown, smooth, scales usually with a fringe of hairs; leaves usually 

 appearing in pairs, ovate to oblong-ovate, 4-14 cm. (l/^-5j^ inches) 

 long, taper-pointed, oblique and wedge-shaped, rounded or slightly 

 cordate at the base, 7-15 pairs of lateral veins, usually 9-11, sharply 

 and rather coarsely serrate, hairy on both sides when they appear, 

 becoming at maturity dark green and somewhat smooth above, 

 usually with a few long hairs remaining, occasionally entirely smooth, 

 paler and more or less hairy on the veins beneath, both surfaces 

 covered more or less with resinous dots; petioles permanently hairy, 

 generally 10-12 mm. (about Y2 inch) long; flowers appear in May, 

 staminate catkins in clusters at the ends of the branches, about 6 

 cm. i^Yi inches) long, scales broadly ovate, blunt, fringed with 

 hairs, green tipped with a margin of reddish-brown, pistillate spikes 

 sohtary in the axils of the leaves, 2-4 cm. i^A-^Yi inches) long, gen- 

 erally about 3 cm. (about 1 inch) long, commonly about half as 



