62 Principles of Plant Culture. 
Section VII. THe Root AND THE SOIL 
With the out-door cultivator, the part of the plant envi- 
ronment that lies beneath the soil surface is more under 
control than the part that lies above it. He can do little to 
change the composition or temperature of the air, or the 
amount of sunlight; he may do much to influence the 
fertility, the texture, the drainage and the aeration of the 
soil. A knowledge of the roots of plants, and of the soil in 
in which they grow and feed is, therefore, of the utmost 
practical importance. 
S7. The Root’s Office. The roots of land plants serve, 
1st,— to anchor the plant in the soil, enabling the stem or 
stems of erect species to grow upright, and, 2d,— to supply 
the plant with water with its dissolved food materials (63). 
SS. The Root Originates in the Stem. As we have 
seen (41), the primary root develops from the lower or 
“root-end”’ of the hypocotyl. But lateral roots may develop 
freely from other parts of the stem. If we examine the 
base of the stem of a plant of Indian corn, a few weeks after 
planting, we may see that the main roots start out above the 
point at which the stem was originally attached to the seed; 
and if we pull up a pumpkin vine or an untrellised tomato 
plant, late in summer, we often find it rooted from the stem 
at some distance from the original root. Lateral roots 
originate in the internal tissues of the stem or root, and not 
upon the surface as do buds (132). 
89. Moisture Excites Root Growth. Roots develop, 
as a rule, from portions of the stem that are maintained for 
a certain time in contact with abundant moisture. In the 
