KEY TO GENERA AND SPECIES 27 



45. Leaf base very unsymmetrical, as a rule, and 

 the margins doubly toothed. Fruit flat, 

 with a broad wing surrounding the single 

 seed. (See Fig. 178.) Elm, 144. 



45. Leaf base symmetrical, or nearly so. (See 



Fig. 1 53 -)-46- 



46. Margins with coarse teeth or angles, less than 



6 per inch, or else with straight side veins, 

 each terminating in a bristle-like tooth. 

 (See Figs. 146, 172.) 47. 



46. Margins with small teeth, more than 6 per 



inch. (See Figs. 49, 131.) 49. 



47. Fruit a nut; one to several nuts completely 



enclosed in a prickly bur until mature. Each 

 of the numerous side veins of the leaf-blade 

 terminating in a marginal tooth 48. 



47. Fridt a nut with its base set in a scaly cup. 



Leaf margins commonly with a few large 

 angular teeth or shallow angular lobes, each 

 tipped with a short bristle Oak, 126. 



48. Xut triangular in section. Bark of trunk 



smooth, firm, and gray Beech, 122. 

 48. Xut not triangular in section. Bark of older 

 trunks furrowed Chestnut, 125. 



