104 PLANT LIFE 
what a thin, cord-like organ the ordinary 
young root is. 
Farther back from the growing point the 
mechanical function of the root, as already 
stated, is that of holding the plant in the soil. 
The most effective position for the mechanical 
tissue to occupy to withstand pulls from 
various directions is along the centre or axis 
of the organ. For in this position the stress 
is most evenly distributed. Indeed, the me- 
chanical strands may be regarded as cables 
in this form of construction. 
Sometimes it happens that a root has to 
discharge still more complex mechanical 
functions, and its structure in this respect 
may then vary accordingly. The Indian corn 
plant, for example, has a thick stem, large 
leaves, and heavy fruit (Fig. 14). The rooting 
end where it penetrates the ground is quite 
thin, and the plant is obviously top-heavy, 
but a circle of roots springs from each of 
the nodes of the stem, that succeed each other 
at very short intervals just above the level 
of the ground, and each root grows towards 
the soil in a more or less arched manner; 
in this way the plant as a whole is well 
supported by means of a series of arched 
struts which admirably enable it to over- 
come the mechanical disadvantages of its 
original conformation. Now it is clear that 
when the plant is exposed to a force tending to 
bend it, the roots on the side towards which 
it inclines to fall over are exposed to crushing 
