. Practical botany. Botany. 76 PEACTICAL BOTANY 68. Air storage in stems and leaves. In many marsh and water plants very extensive supplies of air are stored in the interior of the roots, rootstocks, the ordinary stems, and the leaves. This stored air consti- tutes what has been well called an mner atmosphere, by means of which the respiration of the plant is much aided, especially at times when the whole plant body is temporarily submerged. In those marsh or water plants which have the most extensively developed air passages and cav- ities they form a complex system which extends all the way
. Practical botany. Botany. 76 PEACTICAL BOTANY 68. Air storage in stems and leaves. In many marsh and water plants very extensive supplies of air are stored in the interior of the roots, rootstocks, the ordinary stems, and the leaves. This stored air consti- tutes what has been well called an mner atmosphere, by means of which the respiration of the plant is much aided, especially at times when the whole plant body is temporarily submerged. In those marsh or water plants which have the most extensively developed air passages and cav- ities they form a complex system which extends all the way from the stomata to the tips of the roots. Often a large part of the bulk of the plant body is occu- pied l)y such air cavities, sur- rounded by slight walls of solid material. In the leaves of Pistia, a iioating aquatic belonging to the Arum family, 71 per cent of the volume is occupied liy air spaces, while m ordinary land plants these spaces may occupy less than 7 per cent of the total volume of the leaf. An important mechanical use is often subserved by stems or leaves inflated with air, in buoy- ing up the plant, as is well shown by the duckweeds, the \'\-ater liyacinth ( I'/n'Mnrnici), and the ^vat^â r chestnut (^Tnijui). j\Iany seaweeds, as the rockwced, are thus liuoyed Fig. 62. A century plant, nearly ready to blossom The flower stalk considerably devel- oped and the outer leaves beginning to shrivel and droop from loss of food transferred to the flower stalk. Photograph by G. D. Fuller. 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 Bergen, Joseph Y. (Joseph Young), 1851-1917; Caldwell, Otis William, 1869- joint author. Boston, New York [etc. ] Ginn and company
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