DEPTH AND SPREAD OF ROOT SYSTEMS 141 
gions of the stem is of much service in plant propagation. When 
canes of some varieties of Raspberries bend over and touch the 
ground, they become rooted at their tips. If the canes are cut, the 
rooted tip then becomes a new plant. This is a common method 
of propagating Raspberries. If the branches of the Grape Vine, 
or, if many of our shrubs are bent to the ground and a portion 
covered with soil, roots will develop on the buried portion, which 
thereby becomes a means of obtaining new plants. Geraniums, 
Coleus, Roses, and many other plants are propagated by cutting 
off branches and setting them in moist sand where they develop 
adventitious roots and become new plants. 
Depth and Spread of Root Systems.'— Roots must go deep 
enough and spread far enough laterally to meet the demands of 
the plant for absorption and anchorage, both of which in general 
must conform to the size of the shoot. On this account, trees 
need a deeper and wider root system than a Corn plant. But 
aside from these differences which relate to the size of the shoot, 
root systems of different plants differ in the depth and spread 
according to: (1) the conditions of the soil in relation to moisture, 
mineral matter, and air; (2) the type of root system; and (3) the 
difference in the disposition of the roots of different plants, al- 
though similar in type. 
Roots, like all other plant portions containing living cells, 
must have oxygen for respiration. For this reason the region of 
the soil just under the surface where air is accessible is more fav- 
orable for root activity than the deeper soil regions. Besides, 
more of the necessary mineral matter is available in the surface 
layers of the soil. Consequently, root systems increase by ex- 
tending proportionately much more laterally than downward, 
except in cases where there is extensive development of a tap- 
root, as in such plants as Alfalfa and the Mesquite. 
Studies made of the roots of Corn show that under ordinary 
conditions the roots extend laterally, most of them being only 
from 3 to 6 inches under the surface, until they reach a distance 
of about 14 feet from the plant, and then they extend downward 
as well as laterally, often having a depth of 3 or 4 feet when the 
1 The Roots of Plants. Bulletin 127, Kansas Agr. Exp. Sta. Root Sys- 
tems of Ficld Crops. Bulletin 64, N. Dakota Agr. Exp. Sta. Corn, its Habit 
of Root Growth, Methods of Planting and Cultivating, Notes on Ears and 
Stools or Suckers. Bulletin 5, Minnesota Agr. Exp. Sta. 
