ANGIOSPERM TREES 



281 



lateral buds, closely appressed to the branches, are each covered 

 by a single hood-like scale. The small flowers are borne in catkins 

 which are conspicuous only because they appear before the leaves 

 (fig. 198). Of the sixty five willows native to North America, only 

 about twenty five grow to be trees; of these only a few are of 

 importance to man. They range from the tropics northward to the 



Fk;. 1 



)ws are common along river banks. 



limits of tree growth within the Arctic circle and all require con- 

 siderable moisture, being common along stream banks, in 

 swamps, and on springy hillsides (fig. 199). 



Most of the commercial willow timber is produced by one 

 species, the black w^llov^ and its varieties which range from 

 Nova Scotia south and west to the Dakotas and Texas, including 



