. A practical course in botany, with especial reference to its bearings on agriculture, economics, and sanitation. Botany. RESPONSE OP THE PLANT TO ITS SURROUNDINGS 281 Drawing their nourishment from the loose soil in which they are anchored, and lacking the support of a liquid medium, they develop roots and vascular stems. The roots of plants growing in swamps have difficulty in obtaining proper aer- ation on account of the water, which shuts off the air from them; hence they are furnished with large air cavities, and the bases of the stems are often greatly enlarged, as in the Ogeechee lime
. A practical course in botany, with especial reference to its bearings on agriculture, economics, and sanitation. Botany. RESPONSE OP THE PLANT TO ITS SURROUNDINGS 281 Drawing their nourishment from the loose soil in which they are anchored, and lacking the support of a liquid medium, they develop roots and vascular stems. The roots of plants growing in swamps have difficulty in obtaining proper aer- ation on account of the water, which shuts off the air from them; hence they are furnished with large air cavities, and the bases of the stems are often greatly enlarged, as in the Ogeechee lime (Nyssa capitata) and cypress, to give room for the formation of air passages. The peculiar hollow pro-. Fig. 418.—A Southern cypress swamp, showing on the left the peculiar enlarge- mentsfor aeration, known as " cypress ; (From Mo. Botanical Garden Rep't.) jections known as " cypress knees " are arrangements for aerating the roots of these trees. 320. Xerophyte societies are adpated to conditions the reverse of those affected by hydrophytes. The extreme of these conditions is presented by regions of perennial drought, like our Western arid plains and the great deserts of the in- terior of Asia and Africa. Under these conditions plants have two problems to solve, — to collect all the moisture they can and to keep it as long as they can. Hence, plants of such regions have a diminished evaporating surface, owing to the absence of foliage and the compacting of their tissues. 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 Andrews, Eliza Frances, b. 1840; Lloyd, Francis Ernest, 1868-1947. ed. New York, Cincinnati [etc. ] American book company
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