THE BIRCHES 

 GENUS BETULA, LINN. 



TREES with smooth bark marked with conspicuous horizon- 

 tal slits (lenticels), usually curling back in thin horizontal 

 layers. Leaves simple, alternate, deciduous, serrate, stalked. 

 Flowers monoecious, in catkins. Fruit cone-like, scaly; seed 

 flat, winged; 



KEY TO SPECIES 



A. Bark chalky white, yellow beneath. 

 B. Leaves triangular, bark close. 



(B. populifolia) WHITE BIRCH 



BB. Leaves ovate; bark separating freely into layers. 

 (B. papyriferd) CANOE BIRCH 

 AA. Bark gray, curling back, yellow beneath. 



(B. luted) YELLOW BIRCH 



AAA. " Bark red, curling in thin ribbons; cones ripe in June. 

 (B. nigrd) RED BIRCH 

 AAAA. Bark dark brown, lustrous. 



B. Twigs aromatic; bark separating into thick 

 plates. (B. lento) SWEET BIRCH 



6* 



