152 TREES OP THE NORTHERN UNITED STATES 



There is no attempt in the Key to characterize the hy- 

 brids, of which some are quite extensively distributed. 

 Quercus heterophylla, Michx. (Bartram's Oak), supposed to 

 be a hybrid between Quercus Pkellos and Quercus rubra, 

 is found quite frequently from Staten Island southward 

 to North Carolina. 



* Cultivated Oaks from the Old World; bark rough ; leaves more or 



less sinuated or lobed. (A. ) 

 A. Acorn cup not bristly 20. 



A. Acorn cup more or less bristly 21. 



* Wild species, occasionally cultivated. (B. ) 



B. Leaves entire or almost entire, or merely 3- (rarely 5-) lobed 

 at the enlarged summit. (0.) 



. C. Ends about equal, petioles very short. (D.) 



D. Leaves small (2 to 4 in. long), evergreen, bark smooth, 



black (Live-oaks) 10. 



D. Leaves not evergreen in the North, somewhat awned 

 when young, bark very smooth, black and never cracked 

 (Willow-oaks). (E.) 



E. Down on the under side quite persistent 18. 



E. Under side soon smooth 19. 



C. Widened near the tip, somewhat obovate and the end usu- 

 ally 3-lobed ; bark quite black, smooth or furrowed, but 

 never scaly (Black-oaks). (F.) 



P. Leaves acute at base 16. 



F. Leaves abrupt or cordate at base 17. 



B. Leaves distinctly straight-veined, sinuate rather than lobed, 

 the teeth generally rounded and never awned ; bark white, 

 rough and scaling (Chestnut-oaks). (G-.) 

 G. Lobes rounded 5, 6, 7. 



0. Lobes rather acute 8, 9. 



B. Leaves coarsely lobed, the lobes usually rounded, never 



awned; bark white or whitish-brown, cracking and scaling 



off in thin laminae (White Oaks). (H.) 



H. Leaves crowded at the ends of the branchlets 4. 



H. Leaves not crowded ], 2, 3. 



B. Leaves more or less lobed, the lobes and teeth acute and 



bristle-pointed; petiole slender; base rather abrupt; bark 



dark-colored, smooth or furrowed, but never scaly (Red 



Oaks). (I.) 



1. Leaves smooth both sides, at least when mature. .11, 12. 13. 

 J. Leaves soft-downy beneath 14, 15. 



