SALICACEAE 



Quaking Aspen. Poplar 



Populus tremuloides Michx. 



HABIT. A small tree 50-60 feet high and 1-2 feet in diameter; 

 loose, rounded crown with slender branches. 



LEAVES. Semiorbicular or broadly ovate; n/i-3 inches in 

 diameter; yellow-green; apex acute; base rounded; finely 

 crenate-serrate with glandular teeth; thin and firm; glabrous; 

 petioles flattened, n/2-3 inches long. 



FRUIT. Capsules narrowly conical; K inch long; curved; 

 2-valved; gray-hairy. Seed; light brown, \{2 inch long. 



TWIGS. Slender; round; bright red-brown and lustrous, be- 

 coming gray. Winter buds; terminal H^Vi inch long, conical, 

 sharp-pointed, red-brown, sometimes slightly resinous. 



BARK. Smooth; green-white to cream-colored. 



SILVICAL CHARACTERS. Canadian and Hudsonian 

 zones; reproducing vigorously on cut-over or burned-over areas 

 and forming a protective canopy for more tolerant species. 



BiGTooTH Aspen 



Populus grandidentata Michx. 



This medium-sized tree differs from quaking aspen in having 

 coarsely sinuate-toothed leaves 2-5 inches long, stout twigs, 

 and puberulous, dusty-gray buds Vs inch long. 



* * * 



The following European forms have become naturalized in 

 parts of the United States. Their distinguishing features appear 

 in the key: 



1. White poplar, P. alba L., is a large, widely planted tree. 



2. Gray poplar, x P. canescens (Ait.) Sm., is a hybrid of alba x tremula. 



3. Black poplar, P. nigra L., is a wide-spreading tree. 



4. Lombardy poplar, P. nigra var. italica Muenchh., is a hybrid clon of 

 narrow columnar crown and ascending branches which is widely 

 planted. 



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