Absorption is not the sole function of. In all land plants one very important part of their work is to give firm anchorage. For this reason the burrows into the ground, pushing aside the finer particles of earth, and curving round immovable objects, to resume its original direction once the obstacle is passed.
In trees the fact that the spread of the branches overhead is balanced by the spread of the roots makes for security. In all land plants the delicate root-hairs are a surprisingly important factor in giving the plant a firm grip on the soil, because of the tenacity with which they cling to the soil particles. It is difficult, in fact impossible, to divest a root, by shaking, of the particles of fibre, sawdust, or earth in which it has been growing.
This firm attachment is due to a change that takes place in the wall of the hair when it is in contact with the particles of soil. The wall becomes softened and mucilaginous, so that wall and particle are not merely in contact, but are practically fused together. It is this tenacious hold that partly explains why plants really suffer so little, comparatively speaking, in a drought. Michaelmas Daisies andflowered profusely in the autumn following the summer drought of 1929. Apparently they had not suffered in any way from lack of water, but they had benefited greatly from the extra sun.