THE TREE. 13 
Oak, White Oak, Black Walnut and Butternut. Most of our 
trees have a combination of the two kinds, as the Maple, Hack- 
berry and Ash. Seedling trees of most kinds have a decided tap 
root when young, but in many species it ceases to grow down 
ward 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 
Figure 2. Characteristic Root Formation. On the left two Hackberry, 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. 
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 occu- 
pied 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 have a 
more compact root system than those grown on poor land. 
At the Minnesota Experiment Station a small Bur Oak 
growing on dry, gravelly soil had a tap root that was evidently 
20 feet long, while on moist fertile clay land in the same section 
such trees probably seldom have tap roots more than six feet 
long. 
Buds are placed regularly on the young branches and are 
