17 
90 Teeth 5 or less per inch of margin—Large-toothed Aspen, 
Large-toothed Poplar, Poplar, Popple, Pop ulus grandidentata 
Mx. 
96 Teeth 6 or more per inch of margin—97 
. 97 Leaf-stalk prominently flattened contrary to the blade—9S 
97 Leaf-stalk not flattened, or but very slightly—101 
98 Blade rounded or broadly egg-shaped, usually pointed— 
American Aspen, Quaking Asp, Trembling Poplar, Trem¬ 
ble, Populus tremuloides Mx. 
98 Blade triangular, triangularly egg-shaped, or rhombic—99 
99 Crown of the tree very narrow and spiry. Branches closely 
ascending. Leaves commonly broader than long. Cult. 
—Lombardy Poplar, Populus nigra var. ilalica Du l\oi. 
99 Crown of the tree not spiry—100 
100 Young twigs smooth. Western N. E. and cult.—Carolina 
Poplar, Cottonwood, Necklace Poplar, Cotton-tree, Populus 
delloides Marsh. 
100 Young twigs hairy. Occasionally cult.—Black Poplar, 
Populus nigra L. 
101 Length of blade about twice the width. Northern and 
western N. E.—Balsam Poplar, Tacamahac, Rough-barked 
Poplar, Populus balsamifera L. 
101 Length of blade scarcely greater than the width—102 
102 Apex of the blade blunt or rounded. Conn.—Downy 
Poplar, Swamp Cottonwood, River Cottonwood, Populus 
heterophylla L. 
102 Apex of the blade tapering to a very sharp point. Cult, 
and escaped—Balm of Gilead, Balsam, Populus candicam 
Ait. 
Walnut —Leaves compound. Leaflets averaging 11 to 23. 
Fruit enclosed in a husk which does iiot split open at 
maturity. Nut roughened with sharp points or ridges. 
103 Leaflets 11 to 17, sticky-hairy, as are also the leaf-stalks 
and young fruits. Fruit oblong—Butternut, White Walnut, 
Oilnut, Juglans cinerea L. 
