60 Bulletin 194 



THE POPLARS 



The genus Populus belongs to the willow family and resemble the 

 willows, especially in flower and fruit characters. The nodding, worm- 

 like, staminate and pistillate catkins are borne upon different trees, and 

 opening before the leaves, are conspicuous in early spring. The poplars 

 are distributed quite widely, extending from the Arctic Circle to 

 Mexico and from the Atlantic to the Pacific. 



The wood of poplars is very soft and light and especially liable to 

 warp, but is cheap and useful for making toys, boxes and smaller fur- 

 niture. Much of it now goes to the pulp mills. 



SUMMER KEY TO THE SPECIES OF POPULUS 



a. Leaf-petioles essentially terete. 



b. Petioles and lower sides of leaves pubescent ; leaves heart- 

 shaped P. candicans, p. 71 . 



bb. Petioles and lower sides of leaves glabrous ; leaves ovate- 

 lanceolate P. balsamifera, p. 69. 



aa. Leaf-petioles strongly flattened. 



b. Petioles and lower sides of leaves tomentose; twigs pubescent, 



P. alba, p. 63. 

 bb. Petioles and lower sides of leaves glabrous ; twigs glabrous. 

 c. Leaves distinctly deltoid in shape. 



d. Leaves broader than they are long, abruptly acuminate at 

 the apex ; marginal teeth not conspicuously incurved ; 

 branches erect and more or less appressed to the main stem, 

 forming a narrow, spire-like crown.P. nigra italica, p. 75. 

 dd. Leaves longer than they are broad, more or less taper- 

 pointed at the apex; marginal teeth rather conspicuously 

 incurved ; branches spreading, forming a broad crown. 



P. deltoides, p. 7Z. 

 cc. Leaves ovate to nearly orbicular in shape. 



d. Margin of leaves coarsely sinuate-toothed ; leaves 3-5 inches 



long P. grandidentata, p. 67. 



dd. Margin of leaves finely serrate ; leaves less than 3 inches 

 long P. tremuloides, p. 65. 



