THE TREE. 9 



of taking- up the water and plant food; the older roots are 

 most useful in holding- the tree in place. It is common to 

 classify roots into surface roots and tap roots depending- on 

 their shape and the depth they g-o in the ground. Some trees 



Figure 2. Characteristic Root Formation. On the left two Hack- 

 berry, on the right two White Birch, each 2-year seedlings from same 

 seed bed. The first with a divided tap root, the second without tap 

 root. 



have nearly all surface roots, as the Birch and Spruce; others 

 have nearly all tap roots which often go to a great depth on 

 dry land as those of the Bur Oak, White Oak, Black Walnut 

 and Butternut. Most of our trees have a combination of the 

 two kinds, as the Maple, Hackberry and Ash. Seedling trees 

 of most kinds have a decided tap root when young- but in 

 many species it ceases to grow downward when a few years 

 old. This is true of the Red and Scarlet Oaks which often 

 have a tap root extending- four feet in depth before the tree 

 has attained a corresponding- height above ground but after 

 about five years large lateral roots develop and the growth 

 of the tap root nearly ceases. 



Root growth is relatively less to the extent of ground oc- 

 cupied in moist and fertile soil than in dry and poor soil but 

 the roots are proportionately more branched. In wet seasons 

 the root development is less for a given plant than in dry 

 seasons because the roots may get their needed food and water 

 from a small area. Nursery trees grown on moist rich land 



