52 TREES OF THE NORTHERN UNITED STATES 



In the description of leaves the dimensions given refer 

 to the blade. 



KEY TO THE GENERA OF TREES. 



* Leaves narrow linear, needle, scale or awl shaped, usually but 



not always evergreen. (GG. ) page 60. 



* Leaves broad, flat, usually deciduous, occasionally evergreen, 



rarely over 5 times as long as wide. (A.) 

 A. Leaves alternate, 1 simple. (B.) 

 A. Leaves alternate, compound, (m.) page 57. 

 A. Leaves opposite or whorled on the stem, (u.) page 58. 

 B. Leaves with a midrib, netted-veined. (C.) 



B. Leaves without a midrib, parallel-veined 109. Salisburia. 



C. With radiating ribs, and including those which have the 

 lower ribs longer and more branching than those above 

 them. (f. ) page 56. 



C. With distinct and definite feather- veining. (D.) 

 D. Margin entire, or so nearly so as to appear entire, sometimes 



slightly angulated but not lobed. (V.) 

 D. Once or twice serrate or crenate or wavy-edged, but not lobed. 



(E.) 

 D. Distinctly lobed. (S.) (If the notches are over 10 on a side, 



look under E. ) 

 E. Straight-veined. (M.) 



E. Not distinctly and evenly straight-veined. (F. ) 

 F. Leaves evergreen with either revolute or spiny-tipped mar- 

 gins 18. Ilex. 



F. Leaves evergreen, lanceolate-oblong, minutely serrate ; flowers 



white, 4 in. in diameter 8. Gordonia. 



F. Leaves deciduous. (G.) 

 G. Fruit with fleshy and often edible pulp. (K.) 

 G. Fruit a dry and more or less rounded pod. (H.) 

 G. Fruit and flowers in dry catkins; leaves, in most species. 3 

 or more times as long as wide, finely serrate to entire, with 

 free stipules, in many species remaining on the young twigs, 

 in others shown by a rounded scar on the sides of the stem ; 



wood soft ; the Willows 91. Salix. 



G. Fruit dry akenes with silky pappus, in small heads ; whole 

 plant whitened with scurf ; leaves broadened and coarsely 

 notched near tip ; a broad spreading bush. . . .49. BaccJiaris. 



1 Look on the elongated branches for the arrangement of the leaves ; they 

 are too closely clustered on the short side shoots. See page 18. 



