. Principles of modern biology. Biology. 610 - Heredity and Evolution. Fig. 31-17. Corn, infected by corn smut (Ustilago zeae), another parasitic basidiomycete. (Photo by Benjamin Koehler; from The Plant World.) groups, especially the gymnosperms and angiosperms, finally did evolve a fertiliza- tion mechanism in which the sperm do not need water while they are being transmitted to the eggs (Chap. 12). Plant Embryos and Their Protection. The sec- ond problem—nurturing the zygote during the early vulnerable stages of development— began to reach a solution very early. All Em- bryophyta (see below
. Principles of modern biology. Biology. 610 - Heredity and Evolution. Fig. 31-17. Corn, infected by corn smut (Ustilago zeae), another parasitic basidiomycete. (Photo by Benjamin Koehler; from The Plant World.) groups, especially the gymnosperms and angiosperms, finally did evolve a fertiliza- tion mechanism in which the sperm do not need water while they are being transmitted to the eggs (Chap. 12). Plant Embryos and Their Protection. The sec- ond problem—nurturing the zygote during the early vulnerable stages of development— began to reach a solution very early. All Em- bryophyta (see below) are characterized by the possession of multicellular reproductive organs. Especially important are the arche- gonia (p. 205). In the archegonium, the zygote and the developing embryo are pro- tected and nurtured until the young plant can shift for itself. This development is the primary basis for grouping all terrestrial species into one large subkingdom—the Sub- kingdom Embryophyta. All members of this large group possess multicellular archegonia, in which the embryos develop. Also all Em- bryophyta possess multicellular sperm-form- ing organs (antheridia) and multicellular spore-forming organs (sporangia). And lastly, the Embryophyta all display a regular alter- nation between the diploid asexual sporo- phyte generation and the haploid sexual gametophyte generation (Chap. 12). The Bryophyta (Literally, Moss Plants). This phylum (about 23,000 species) of rela- tively small primitive land plants includes two classes: (1) the Hepaticae, or liverworts (Fig. 13-4), and (2) the Musci, or true mosses Fig. 12-11).. 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 Marsland, Douglas, 1899-. New York, Holt, Rinehart and Winston
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