CHAPTER XX: THE POPLARS 



Family Salicace/^ 

 Genus POPULUS 



Quick-growing trees with angled or round twigs, set with 

 scaly buds, soft, light wood, and bitter bark. Leaves deciduous, 

 simple, alternate, usually broad, on long petioles. Flowers 

 dioecious, both kinds in crowded, pendulous catkins; each flower 

 subtended by a bract with deeply cut, hairy margin. Fruit 

 pendulous racemes of 2 to 4-valved pods; seeds minute, with dense, 

 silky float attached. 



KEY TO SPECIES 



A. Leaf stalks flattened. 



B. Buds smooth, resinous. 



C. Leaves triangular, coarsely serrate. 

 D. Blades of leaves 3 to 5 inches long. 



(P. deltoidea) Cottonwood 

 DD. Blades of leaves 2 to 2| inches long. 

 E. Twigs slender, pubescent, yellow. 



(P. Fremontii) cottonwood 

 EE. Twigs stout, smooth, orange. 



{P. Wisliieni) cottonwood 

 CC. Leaves roundish, finely serrate. 



(P. tremuloides) quaking asp 

 BE. Buds downy; leaves ovate, coarsely toothed. 



(P. grandideniaia) great-toothed aspen 

 AA. Leaf stalks round; buds resinous. 

 B. Foliage green on both sides. 

 C. Shape of leaves lanceolate. 



(P. angustijolia) narrow-leaved cottonwood 

 CC. Shape of leaves rhombic or deltoid, with long- 

 pointed apex. 

 D. Margins finely serrate. 



(P. acuminata) lance-leaved cottonwood 

 DD. Margins coarsely and crenately toothed. 



(P. Mexicana) Mexican cottonwood 



45 



