Elements of biology; a practical Elements of biology; a practical text-book correlating botany, zoology, and human physiology elementsofbiolog00hunt Year: [c1907] 144 BOTANY Plants living in water have loose and spongy tissues; many large intercellu- lar spaces are found in stems or leaves. In one pond lily (Nelumbo lutea) these spaces in the leaf communicate with large spaces in the veins of the leaf, and these in turn with spaces in the petiole, stem, and root, so that all parts of the plants are in communication with the air above. The roots of a plant living wholly in water are not needed
Elements of biology; a practical Elements of biology; a practical text-book correlating botany, zoology, and human physiology elementsofbiolog00hunt Year: [c1907] 144 BOTANY Plants living in water have loose and spongy tissues; many large intercellu- lar spaces are found in stems or leaves. In one pond lily (Nelumbo lutea) these spaces in the leaf communicate with large spaces in the veins of the leaf, and these in turn with spaces in the petiole, stem, and root, so that all parts of the plants are in communication with the air above. The roots of a plant living wholly in water are not needed for sup- port, hence they arc often short and stumpy. They do not need to be modified to absorb water; consequently the absorbing surface lacks root hairs. The whole plant, when under water, is usually modified to take water (and with it food) from its immediate en- vironment. Hydrophytes. — If water is pres- ent in such quantity as to satu- rate the soil in which the plant lives the conditions of its en- vironment are said to be hydrophytic and such plant is said to be a hydrophyte. Xerophytes. — The opposite of hydrophytic conditions is seen when the soil is very dry. Such a condition is known as xerophytic, and the plants liv- ing in these conditions are xerophytes. Such is the con- dition in a desert. We have seen that the most important adaptations of xerophytes are such as prevent evaporation of water from their bodies. The leaf surface is reduced, the leaves being changed into spines as in the cactus, or very greatly reduced in size, as in the switch plants of our alkali A water plant, showing the finely divided leaflike pax'ts.
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