54 
THE VEGETATIVE FUNCTIONS OF PLANTS 
49. Relation between the Water and the Soil. Fig. 
43 is a diagram, showing on a greatly enlarged scale, 
how the root-hairs lie in the soil, and the condition of the 
soil most desirable for the well-being of the plant. It 
is seen from the figure that the soil is not compact, but 
open or porous, the soil particles being separated by 
spaces as large or larger than themselves. Under con- 
ditions most favorable for the plant, the spaces are 
FIG. 43. Diagram to illustrate a root-hair (h) in the soil, and its 
relation to the soil-particles, the capillary film of water (w), and the air 
spaces (a); e, epidermal cell of the root, of which the root-hair is an out- 
growth, or branch. (After Sachs.) 
filled with air, while each particle of soil is surrounded by a 
thin film of water. This is the water that supplies the 
plant through the root-hairs. As fast, as removed it is 
replenished by the capillary action of the soil. Roots 
will continue to remove the capillary water from the soil 
until a point is reached where the attraction of the soil- 
particles for the water exceeds the absorbing power of the 
root-hairs; then the plant will wilt unless more water is 
added. Plants cannot absorb all the water from the soil. 
