. Science of plant life, a high school botany treating of the plant and its relation to the environment. Botany. The Ferns and Their Allies 291 can be transmitted from one part to another only slowl}- by diffusion from cell to cell. They have no water-conducting. Fig. 173. The life history of a fern. The prothallus (-4) produces egg cells and sperms in organs on the lower surface. One of the sperms set free from B unites with an egg cell (shown in C), and produces a sexual spore. This germinates and produces the leafy fern plant (D), which in turn produces asexual spores in sporangia (P and G)
. Science of plant life, a high school botany treating of the plant and its relation to the environment. Botany. The Ferns and Their Allies 291 can be transmitted from one part to another only slowl}- by diffusion from cell to cell. They have no water-conducting. Fig. 173. The life history of a fern. The prothallus (-4) produces egg cells and sperms in organs on the lower surface. One of the sperms set free from B unites with an egg cell (shown in C), and produces a sexual spore. This germinates and produces the leafy fern plant (D), which in turn produces asexual spores in sporangia (P and G) on the lower side of the leaves. By the bursting of the walls of the sporangium (H), the spores are set free. They then germinate on the soil (in some species on rocks or trees) and produce a new generation of prothaJli Hke the one shown in A. The pro- thallus is here shown about 4 times its natural size. or food-conducting tissues, and for this reason they are all of small size. The development of a conductive system is, therefore, an additional step in the complete adjustment of plants to a land environment. With a conductive system, the water may be carried rapidly from one part of a plant to another. Con- sequently stems and leaves may be raised far above the groimd level and yet receive sufficient water from the roots to replace that lost through transpiration. Likewise an adequate supply of food may be transferred to the roots, which makes it pos- sible for them to Hve in the soU, where they are unable to. 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 Transeau, Edgar Nelson, 1875-1960. Yonkers-on-Hudson, N. Y. , World Book Co.
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Keywords: ., bookcentury1900, bookdecade1920, booksubjectbotany, bookyear1921
