Nature and development of plants . I 3b Fig. 256. Development of the young sporophyte or embryo: 2, diagramof a section of a megasporangium, showing the formation of elongatedsuspensory cells and numerous embryos, e; i, integument; sp, sporangiumnearly consumed by the growth of the gametophyte; g, gametophyte, thecentral portion of it disorganized by growth of embryos, e. 3A, section ofa nearly mature embryo; s, suspensor; r, root cap; c, cotyledons; st, ,B, external view of embryo. increases in size and the integuments become modified into ahard coat, or the outer layer may be pulpy, as
Nature and development of plants . I 3b Fig. 256. Development of the young sporophyte or embryo: 2, diagramof a section of a megasporangium, showing the formation of elongatedsuspensory cells and numerous embryos, e; i, integument; sp, sporangiumnearly consumed by the growth of the gametophyte; g, gametophyte, thecentral portion of it disorganized by growth of embryos, e. 3A, section ofa nearly mature embryo; s, suspensor; r, root cap; c, cotyledons; st, ,B, external view of embryo. increases in size and the integuments become modified into ahard coat, or the outer layer may be pulpy, as in some of thecycads. The gametophyte also increases in size, and as the em-. Fig. 257. Sectional view of pine seed: /. hard integument; g, gameto-phyte, often called the endosperm, which has completely consumed thesporangia! tissues. The embryo consists of a root, r, ensheathed in alarge root cap. cotyledons, r, and stem, s. DEVELOPMENT OF PLANTS 34i bryo matures it absorbs all the tissues of the sporangium, thusfilling the space within the integument (Fig. 257). The cellsof the female gametophyte are often called the these growths the seed is formed and prepared for its dor-mant state, as in the preceding order. In some cases the integu-ment forms a membranous outgrowth, which assists in the dis-tribution of the seeds (Fig. 258, C). It is interesting to note
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