FECIINDA'TION, or FERTILIZATION, in plants, takes place according to laws similar to those which prevail in the animal kingdom. In plants, however, the organs of repro duction are not permanent as in animals, but fall off—the male organs generally soon .after fecundation, the female after the ripening of the seed. The male seminal sub stance, called pollen, never exists in a fluid state, but always in that of granules of various forms (pollen grains), which consist each of one cell, whose covering is of various thickness, and contains the impregnating substance. After the dehiscence of the anthers, the pollen gets into contact with the stigma of the pistil, which in its lowest and thick est part (the ovary or germen) contains the rudiments of the future seeds (ovules). The inner layer of the cell-covering of the pollen grain separates from the outer and thicker layer, as if it came out of a bag, and continuing to be elongated by growth, is carried down through the style to the germen, where it reaches the foramen or small opening of the embryo sac, and comes into contact with the ovule. or even in many cases penetrates into the ovule itself between its cells. By this time, one or other of the cells of the ovule has become considerably more enlarged than the other cells, and what is called the amnion has been formed, in the mucilaginous fluid of which (protoblasma), after the contact of the pollen-bag, through the dynamic operation of its contents, a cell-germ or cytoblast is soon developed. 'This cytoblast is the first
commencement of a new and distinct. cell, which divides into two cells. These increase, by continually repeated separation of new cells, into a cellular body, which forms the more or less perfect embryo of a new plant. If the organ from which the pollen has proceeded, and the organ which contained the ovule, belong to the same plant or to plants of the same species, the embryo arising from this fecundation becomes a plant of the same species. But if the pollen by which the fecundation is affected comes from a plant of another species than that to which the plant belongs in whose germen the embryo is formed, the seed resulting from this fecundation will not, when it grows, produce plants of the same species, but hybrids, intermediate between the parent plants, and with various degrees of resemblance to one or other of them, but not perfectly corresponding with either. Hence the production of hybrids, and multiplication of varieties of plants in gardens, by what is called the artificial impreg nation of the stigma of one plant with the pollen of another, which, however, must be of an allied species, hybridization being confined by the laws of nature within very narrow limits. See REPRODUCTION.