. Elementary biology; an introduction to the science of life . The inside of the ovule is a soft mass, made up of many compartments, or cells, containing the jellylike living matter, or protoplasm. One of these cells, usually near the center, is much larger than the others (see es, Fig. 134). Within this large cell, called the e^nbryo sac, the protoplasm divides and grows, becoming a young plant, or embryo, inside the seed. The rest of the ovule becomes the coat, or covering, of the embryo. 354. Fertilization. Before the ovule can become a seed, certain changes must take place in the living ma
. Elementary biology; an introduction to the science of life . The inside of the ovule is a soft mass, made up of many compartments, or cells, containing the jellylike living matter, or protoplasm. One of these cells, usually near the center, is much larger than the others (see es, Fig. 134). Within this large cell, called the e^nbryo sac, the protoplasm divides and grows, becoming a young plant, or embryo, inside the seed. The rest of the ovule becomes the coat, or covering, of the embryo. 354. Fertilization. Before the ovule can become a seed, certain changes must take place in the living matter of the embryo sac. A nucleus of the em- bryo sac must first unite with the nuclear substance of a pollen grain. The uniting of two nuclei is called fe rtiliza tion. The method by which the two nuclei are brought together is shown in Fig. 134. 355. Seed and fruit. After fertilization the combined nu- cleus, containing protoplasm from two parents, divides into very many cells. The mass absorbs food in large quantities from the parent upon which it is borne, and becomes a baby plant, or embryo (see Fig. 120). The walls of the ovule, sur- rounding the embryo sac, become the seed covers. The ovule with its embryo sac thus changes into a seed. In addition to the food used in the growth of the embryo, the parent plant supplies other food materials that are accumulated either in a mass surrounding the embryo or within the tissues of the em- bryo itself. This surplus food may later be drawn upon by the young plant, after it sprouts and before it is able to maintain itself through the work of its own leaves and roots. Fig. 133. Sections of ovaries Ovaries are of many sizes and shapes. They contain but a single ovule in some species of plants, and in other species they bear hundreds. The ovules are definitely placed in one or more compartments of the ovary
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