. Principles of modern biology. Biology. 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 pos
. Principles of modern biology. Biology. 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).. Fig. 31-18. Reindeer moss (Cladonia rangiferina). These and other lichens can grow on very poor soil and in very cold regions. (From The Plant World.). 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-
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