Birch family 



knife that it has become the favorite tfee for arbor-walks in 

 parks. 



The flowers are monoecious ; the staminate flowers appear 

 in long, loose, pendulous catkins from axillary buds. The pis- 

 tillate, in loose half-erect catkins at the end of the spray. 

 Each pistillate flower is subtended by a bract which expands 

 with the growth of the fruit into a sort of leaf which gathers 

 around and protects a small oval nut. These fruit clusters 

 often remain on the trees long after the leaves have fallen. 



The tree can be easily raised from the seed which does not 

 germinate until the second year. Traces of Carpinus have 

 been found in the tertiary rocks of Alaska and in the upper 

 miocene of Colorado and Nevada, regions from which the 

 genus has entirely disappeared. 



322 



