A curious and characteristic feature of the life-history of the higher forms of plants is the long resting period which takes place in the seed, following the reproductive act, after a certain amount of development. Fertilisation of the female element is succeeded by a period of activity, during which great changes in the oosphere take place, many new cells are formed, and the new individual becomes recognisable. But then comes a remarkable alteration; the development for a time is arrested, no new cells are produced, but those already formed, which constitute chiefly the first leaves or cotyledons of the new plant, become filled with nutrient materials, forming reserves upon which, after the resting period, the young plant will subsist, and which will enable it to resume its growth. Or it may be that the nutrient material may be accumulated in cells immediately surrounding the young embryo, cells which form the so-called endosperm and which are not actually part of it. A curious feature this, not represented exactly by anything in the cycle of animal life, though perhaps the condition of the egg which is deposited by the parent and quickened later into active life approaches somewhat to it. This differs greatly, however, in the length of the quiescent period, which in the seed may be almost indefinitely prolonged. What changes, if any, take place in the cells during this period is not known and cannot well be ascertained. At the end of this time changes do take place, and the arrested development is resumed. That the condition of things inside the seed is not exactly alike always, seems pointed to by the fact that seeds of the same plant do not germinate at all times with equal readiness, though exposed to the same favourable conditions. During this period, long or short as it may be, and its length varies extremely, the different bodies occupying the interior of the cells of the cotyledons or the endosperm maintain their character apparently unchanged, or, if changed at all, the nature of the change is such as not to be recognisable by microscopic examination or by chemical analysis, only being marked by greater or less resistance to the setting up of the manifest changes which are known as the process of germination. The process of deposition of the several reserve products in the cells of the seed has been watched by many observers, and the details of the storage have been examined and traced out step by step. The resumption of the arrested development, under the conditions of moisture and of temperature which we call favourable to germination, involves intricate metabolic processes in which the different materials that have been stored are all separately concerned, each group of bodies being transformed into nearly related ones which are adapted for the new conditions of life. Instead of the resting forms of proteids, carbohydrates, &c., which are not diffusible and hence cannot pass from cell to cell and so traverse the plant, we have new forms which can readily travel to those points where growth is proceeding and new cells are being formed, and hence plastic material is required. The details of these transformations are in many cases still obscure, though some facts have been ascertained which throw light upon the nature of some of the chemical processes. In the case of the starch, which is so constant a constituent in seeds, it has been proved that the formation of sugar takes place from it by the agency of a ferment, exactly as it does in the corresponding process in the animal economy. From almost any seed a so-called diastatic ferment can be obtained, and so constant is the occurrence of the latter body in vegetable organisms that it can be prepared from almost any part of plants. From analogy it would seem probable that the proteolytic changes noticeable would have a similar cause, and that from seeds in which large quantities of reserve proteids are stored evidence of such a body could be obtained.