2 BULLETIN 316, U. S. DEPARTMENT OE AGRICULTURE. 



THE TREE AND ITS FORMS. 



The botanical name of the willow genus, Salix, comes from the 

 Celtic sal, meaning near, and lis, water. The poplar is a genus of 

 the same family. Both have more species and wider distribution 

 in North America than on any other continent, the willows being 

 more widely distributed than the poplars but less generally attaining 

 tree size. 



The fruit of this group is the characteristic by which it is most 

 easily distinguished. In both genera it is a catkin an inch or more 

 long, made up of capsules borne on a stalk and containing a cottony 

 mass to which are attached numerous minute seeds. The catkins 

 of the willow are smaller than those of the poplar and are generally 

 erect; those of the poplar are generally pendant. In both cases the 

 seed has a tuft of silky hairs attached to the base. When the cap- 

 sules open the tiny seeds are borne up by the cottony hairs and 

 carried long distances by the wind. Willow seed consists of the bare 

 embryo or new plant and is protected by a very thin covering. It 

 germinates in a few hours in a moist place; but if it fails to secure 

 this condition, it loses the power of germination in two or three days. 



The willows can be distinguished from the poplars by their leaves, 

 the poplars having typically long-stalked wide leaves; the willows, 

 short-stalked narrow ones. Willow leaves occur alternately on the 

 branches. There are several scales on each winter bud of the poplar, 

 but only one on each willow bad. 



The willows do not normally develop a strong taproot. However, 

 those grown on dry upland situations and some of the drought- 

 resistant species form semitaproot systems. Usually willows grow 

 in moist situations and places where the- water table is near the 

 surface; so the root system is shallow, spreading, and fibrous. 



The bark of the different species of tree -willows is very much the 

 same, and does not furnish an obvious means of distinguishing them, 

 except in the case of the sandbar willow, which has almost smooth 

 bark even in trees of considerable size. 



The characteristics on which botanists separate the species are 

 largely differences in the tiny flowers and the almost microscopical 

 variations in the leaf parts. Several species are easily identified by 

 the size, shape, or color of the leaves, but the majority have very 

 similar gross characteristics. 



BLACK WILLOW. 



(Salix nigra Marsh.) 



The black willow is by far the most important of the native species. 

 In the region of its best development trees have been found 4 feet in 

 diameter at breastheight and 140 feet in height. The leaves are 



