i 3 o KEY TO GENERA AND SPECIES 



193. Leaves 2 to 4 inches long, middle lobe broadly 

 triangular. Merely a form of the Red 

 Maple. New Brunswick and Mass., and 

 local southward and westward. (Fig. 248.) 

 Three-Toothed Red Maple, Acer rubrum 

 var. tridens Wood. 



Fig. 248. Three-toothed 

 Red Maple. 



Fig. 249. Rock Maple. From 

 infertile branch. 



194. Lower surface of the leaf pale and smoothish. 

 Leaves of infertile trees (Fig. 249) differ 

 from those of the fertile or fruiting trees. 

 (Fig. 251.) Throughout our range. (Figs. 

 249, 251, 250.) Rock Maple, Sugar Maple, 

 Hard Maple, Sugar-tree, Acer saccharum 

 Marsh. 



