264 CANADIAN POPLAR: ASPEN 



(l - 5 10 x 2'5 6 cm.) diameter. Base straight, or slightly- 

 cordate or feebly cuneiform with the lower angles rounded : 

 regularly and closely crenate-serrate, with blunt and 

 thickened teeth. Firm, glabrous, green and somewhat 

 shining on both sides (often yellowish green), or paler matt 

 green beneath. Petioles 3 6 cm., compressed, somewhat 

 shorter than the lamina. Young leaves yellowish, covered 

 with deciduous hairs, somewhat silky ciliate and viscous, 

 as are the buds. The petiole and principal veins often 

 red. The leaves on strong suckers may attain 14 16 cm. 

 diameter. Autumn leaves yellow and brown. 



Venation like that of P. tremula, but the meshes 

 irregularly angular, loose and distinct but not very promi- 

 nent. 



$# Shoots angular and grooved. 



Populus Canadensis, Desf. Canadian Poplar. Very 

 similar to the preceding, but the leaves more ciliate, 

 especially when young, and pubescent on the veins 

 beneath, the shoots more angular. Buds viscous. The 

 leaf varies from 6 12 x 5 10 cm. up to 12 x 13 cm. 

 Petiole pubescent, 3 5 cm. long. 



Leaves more or less sub-orbicular. Dis- 

 tinctly paler beneath and devoid of 

 stomata above. Margins not carti- 

 laginous, bluntly crenate-serrate. 



Populus tremula, L. Aspen. Small tree, with pendent 

 trembling leaves and pubescent suckers and buds. Leaf 

 thin and herbaceous, rounded-ovate to sub-orbicular, 

 3 7 x 3 8 cm., on petioles 3 6 cm. long; or, on 

 strong shoots or suckers, much larger, up to 10 15 cm., 

 and more (14 19 x 12 13'5 cm.), ovate, cordate, on 

 petioles up to 8 cm. long; or triangular with rounded 



