Now suppose the same plant with its roots in an unsuitable soil--too dry or too poor in mineral supplies, for instance--the transpiring leaves above cannot obtain sufficient water and salts to supply their needs, but we will suppose hypothetically that they still assimilate under the same ideal conditions as before. The supplies now coming to the cambium are diminished, since the want of water and minerals compels the leaves to put aside any excess of carbohydrates (_e.g._ as stored starch-grains), and the plastic materials which do pass to the cambium so deficient in water cannot be directly utilised, and a starvation period sets in. Consequently the cambium forms less wood, and this will contain fewer and smaller vessels, and so reduce the conducting passages: fewer sieve-tubes also are constructed, and the paths of the water current and food supplies narrowed, which of course reacts on the tissues everywhere. The reserve substances may slowly be dissolved and distributed, however, and considerable quantities be passed in course of time into the roots, which, as opportunity offers, gradually employ them in making new roots, and if the disturbance has not gone too far and the conditions do not become unfavourable, an increased root-supply may by its larger absorbing area gradually establish the former state of equilibrium of functions. But this at the expense of the plant, which is smaller, has fewer leaves and narrower water channels, etc., than a plant not thus checked, and it may take a long time to make up for the loss of time and stature thus incurred. Indeed if the plant is an annual no recovery at all may occur, the reserves passing into fruit and seeds instead of slowly supplying the roots as described. If it be asked, can such a condition of affairs as that described really occur, we have only to think of a transplanted specimen with its roots maimed and put into unsuitable soil, or of plants in the open with feeding roots gnawed by an insect, etc., or of a tree hitherto in equilibrium with its fellows in a plantation suddenly set free by thinning and so forth.