62 WILD FLOWERS AND TREES OF COLORADO 



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. 49. — Narrowleaf Cottonwood (Populus angustijolia). X£ 



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

 of mountain districts. Populus, balsamifera Linn. 



"Balsam Poplar" 

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

 plains region. Populus acuminata Rydb. 



"Lanceleaf Cottonwood" 



