28 KEY TO GENERA AND SPECIES 



49. Bark chalky white or whitish, or (if dark col- 

 ored) with the outer layers of the bark sepa- 

 rable into thin papery layers Birch, in. 



49. Bark not chalky white, nor whitish 50. 



50. Small twigs aromatic when bruised Birch, 1 1 1 . 



50. Small twigs not aromatic when bruised 51. 



51. Leaves taper-pointed. (See Fig. 49.) 52. 



51. Leaves not taper-pointed. (See Figs. 123, 

 137-) 53- 



Fig. 49. Hop 

 Hornbeam. 



Fig. 50. Hop Hornbeam. 



52. 



Surface of the bark brownish, with somewhat 

 shredded flakes or scales. New Brunswick 

 southward and westward. (Figs. 49, 50.) 

 Hop Hornbeam, Ironwood, Leverwood, 

 Hornbeam, Hardback, Ostrya mrginiana 

 (Mill) K. Koch. 



