78 
the apex the persistent stigmas. Trees or shrubs, the bark 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 
ETSIM Pavey 0X01 litres ts chance, oe ame Se ath se ree VN MTA ely cas 1 B. lutea. 
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- 
ingvaments erect OT NearlyesSOng-2 sees eee 2 B. nigra. 
Bark of trees chalky white, not sealy 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 basezolathesimbsensc mer ce ee oe ee 3 B. populifolia. 
Upper surface of leaves not shiny; staminate catkins 
usually 2 or 3; no dark spots on the bark at the 
basevof the limbs-s--..2-2----- EARN aks ice te 4 B. papyrifera. 
1. Betula lutea Michaux. Bircu. 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 em. (114-514 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 14 inch) long; flowers appear in May, 
staminate catkins in clusters at the ends of the branches, about 6 
em. (21% inches) long, scales broadly ovate, blunt, fringed with 
hairs, green tipped with a margin of reddish-brown, pistillate spikes 
solitary in the axils of the leaves, 2-4 em. (34-11% inches) long, gen- 
erally about 3 cm. (about 1 inch) long, commonly about half as 
