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UNIVERSITY OF COLORADO STUDIES 



3a. Leaf-stalk stout; one-third the length of blade or less; blades narrow. 



Populus angustifolia James. 

 "Narrowleaf Cottonwood" 

 3b. Leaf-stalk slender, one-half the length of blade or longer. (4) 



Fig. 5. — Narrowleaf Cottonwood {Populus angustifolia). X£. 



4a. Leaf-blades ovate; rounded at base, under surface whitish; veins prominent. Trees 

 of mountain districts. Populus balsamifera Linn. 



"Balsam Poplar" 

 4b. Leaf -blades lance-ovate, generally narrowed at base. Tree of canyons and the 

 plains region. Populus acuminata Rydb. 



"Lanceleaf Cottonwood" 



