19 
109 Small twigs aromatic when bruised or broken—Black Birch, 
Sweet Birch, Cherry Birch, Betula lento L. 
109 Small twigs not aromatic when bruised. Southern X. K. 
River Birch, Red Birch, Betula nigra L. 
110 Small twigs aromatic when bruised—Yellow Birch, Silver 
Birch, Betula lutea Mx. f. 
110 Small twigs not aromatic when bruised—111 
111 Leaves deeply cut, often into narrow divisions. Cult.— 
Cut-leaved Birch, Betula alba var. dalerarlica L. 
Ill Leaves not deeply cut, distinctly triangular, usually 
with a tapering apex—Gray Birch, White Birch, Poverty 
Birch, Oldfield Birch, Betula populi folia Marsh. 
111 Leaves neither deeply cut nor triangular—112 
112 Young branches perfectly smooth. Northern N. E.— 
White Birch, Blue Birch, Betula pendula Both. 
112 Young branches minutely hairy—113 
113 Branches pendulous.* Cult.—Weeping Birch, Betula alba 
var. pendula Ilort. 
113 Branches not pendulous—114 
114 Leaves rounded or slightly wedge-shaped at base—115 
114 leaves broadly egg-shaped, heart-shaped at base. Nor¬ 
thern N. E.—Cordate-leaved Birch, Betula (dba var. cordi - 
folia (Hegel j Fernald. 
115 Leaves \% to inches long. Cult.—European Paper 
Birch, Betula alba L. 
115 Leaves '1% to ?>% inches long. American Canoe Birch, 
Paper Birch, Canoe Birch, White Birch, Betula alba var. 
papijrifmt (Marsh.) Spach. 
Alder —Shrubby, or occasionally tree-like. Flowers in catkins. 
Fruit clusters cone-like. 
11<> Leaves broadest at the middle or below—117 
110 Leaves broadest above the middle—1 IS 
9 Betula alba var. olutinom (Wallr.) Traut., with pendulous branches, is local 
near Mt. Katulidin, Me. 
