10 
10. 
11. 
12. 
SALICACEAE. 
. Weeping. P. Tremula pendula. 
Fastigiate. 2. 
Neither weeping nor fastigiate. 3. 
. Twigs and plump buds woolly. 
(Bolles’ poplar). P. alba Bolleana. 
Twigs and slender buds glabrous. 
(Lombardy poplar). P. nigra italica. 
. Lateral buds plump, with 4 or more exposed scales. 4. 
Lateral buds often elongated, mostly with 3 exposed 
scales. (Cottonwoods and Balsams). 8. 
. Buds glabrous or glabrate. 5. 
Buds persistently silky or tomentose. 6. 
. Buds glabrous, somewhat gummy. 
(American aspen). (1). P. tremuloides. 
Buds somewhat downy. (European aspen). P. Tremula. 
. Twigs glabrous. (Large-toothed aspen). P.grandidentata. 
Twigs tomentose. 7. 
. Tomentum gray. (Gray poplar). P. canescens. 
Tomentum white. (Silver poplar). ' P.; alba: 
. Buds short and broad, dark and brown. 
(Swamp cottonwood). (2). P. heterophylla. 
Buds elongated, often gummy. 9. 
. Twigs green or gray or buff, glabrous. (Cottonwoods). 10. 
Twigs brown or red-brown, somewhat villous. 
(Balm-of-Gilead). (3). P. candicans. 
Trees oblong, with ascending branches. 
(“Carolina cottonwood’).  P. Eugenei. 
Tree ovoid or open. 11. 
Of moderate growth: twigs rather slender. 
(European black poplar). P. nigra. 
Large: twigs rather stout: native. 12. 
Buds glabrous. (Common eastern cottonwood). 
(4). P. deltoides monilifera. 
Buds minutely velvety: Western. 
(Plains cottonwood). P. Sargentii. 
