. Cytology, with special reference to the metazoan nucleus. Cells; Cytology. MEIOTIC PHASE IN PLANTS 213 At fertilization the two male gamete nuclei which are formed in each pollen grain are both introduced into the embryo-sac ; one fuses with the ovum nucleus to produce the zygote, while the other fuses with the central fusion nucleus, forming thus a triploid nucleus. This afterwards gives rise to the endosperm, or reserve food material of the seed. For a more detailed account of the gametophyte and fertilization in the flowering plants the reader is referred to any comprehensive work on bota

. Cytology, with special reference to the metazoan nucleus. Cells; Cytology. MEIOTIC PHASE IN PLANTS 213 At fertilization the two male gamete nuclei which are formed in each pollen grain are both introduced into the embryo-sac ; one fuses with the ovum nucleus to produce the zygote, while the other fuses with the central fusion nucleus, forming thus a triploid nucleus. This afterwards gives rise to the endosperm, or reserve food material of the seed. For a more detailed account of the gametophyte and fertilization in the flowering plants the reader is referred to any comprehensive work on bota

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. Cytology, with special reference to the metazoan nucleus. Cells; Cytology. MEIOTIC PHASE IN PLANTS 213 At fertilization the two male gamete nuclei which are formed in each pollen grain are both introduced into the embryo-sac ; one fuses with the ovum nucleus to produce the zygote, while the other fuses with the central fusion nucleus, forming thus a triploid nucleus. This afterwards gives rise to the endosperm, or reserve food material of the seed. For a more detailed account of the gametophyte and fertilization in the flowering plants the reader is referred to any comprehensive work on botany, such as that of Bower (1919). Pollen Mother Cell Meiolilc Embryo sac Mother Cell Microspores d, {Pollen-grains)I . Fig. 90. Diagrams of the cell generations involved in the haploid phase of the flowering plants. Mosses and liverworts present the reverse case to the flowering plants, for the dominant phase (the ordinary moss plant, etc.) is the haploid gametophyte. The zygote grows into a comparatively simple sporophyte which is retained on and nourished by the gametophyte, and produces spores with reduction of chromosomes. These are set free to produce the new generation of gametophytes. The relations of the haploid and diploid phases of the life cycle in animals and plants is summarized in Fig. gi ; the figures A-F form a progressive series in the rise of the diploid and reduction of the haploid. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original work.. Agar, Wilfred Eade, 1882-. London Macmillan