. Principles of modern biology. Biology. 212 - Multicellular Planfs tophyte generation retains a capacity to re- produce by sporulation. LIFE CYCLE OF THE MOSSES Mosses, the most familiar of the Bryo- phyta, are small green leafy plants, which grow in densely crowded masses, on damp and shaded soils (Fig. 12-11). Mosses are not well adapted to terrestrial conditions, and most species cannot survive in dry localities. Most mosses are relatively short plants, with an average height of only about half an inch. The small green leafy-stemmed moss plant is a gametophyte—that is, a haploid gamete- pr
. Principles of modern biology. Biology. 212 - Multicellular Planfs tophyte generation retains a capacity to re- produce by sporulation. LIFE CYCLE OF THE MOSSES Mosses, the most familiar of the Bryo- phyta, are small green leafy plants, which grow in densely crowded masses, on damp and shaded soils (Fig. 12-11). Mosses are not well adapted to terrestrial conditions, and most species cannot survive in dry localities. Most mosses are relatively short plants, with an average height of only about half an inch. The small green leafy-stemmed moss plant is a gametophyte—that is, a haploid gamete- producing individual. The crowded leaves all originate from a single central stem, which cannot be seen unless the leaves are plucked away. Numerous rhizoids extend down into the soil horn the lower end of the stem. The rhizoids absorb water and inor- ganic salts for the upper green parts of the plant, which, in return, provide the rhizoids with glucose. Accordingly, the gametophyte of the moss is a small but independent plant, which displays a typically holophytic nu- trition. The antheridia, or archegonia, depending upon the sex of the gametophyte, develop at the top of the stem, hidden by the en- circling upper leaves—Figure 12-12. In the mature female plants, a single large egg cell is found in the venter of each archegonium (Fig. 12-12). The sperm are liberated in swarms (Fig. 12-12) from the antheridia (Fig. 12-12) of the male plants during peri- ods of rain or heavy dew. Each sperm (Fig. 12-12) is a delicate elongate cell possessing two flagella, which enable the sperm to swim through water to a neighboring female plant. Some sort of chemical attraction appears to emanate from the neck of the archegonium, and thousands of sperm may simultaneously attempt to swim down this narrow Fig. 12-11. A clump of moss plants (Polytrichum). The leafy (lower) part of each plant is a gametophyte, from the top of which grows the slender-stalked sporophyte. The conspicuous wh
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