. Introduction to structural and systematic botany, and vegetable physiology. Botany. 148 THE LEAVES. ferent is the organization of tlie two strata, that a leaf soon perishes if reversed so as. to expose the lower surface to direct sunshine. 264. A further and more effectual provision for restraining the perspiration of leaves within due limits is found in the Epidermis, or skin, that invests the leaf, as it does the whole surface of the vege- table (69), and which is so readily detached from the succulent leaves of such plants as the Stonecrop and the Live-for-ever (Sedum) of the gardens. The
. Introduction to structural and systematic botany, and vegetable physiology. Botany. 148 THE LEAVES. ferent is the organization of tlie two strata, that a leaf soon perishes if reversed so as. to expose the lower surface to direct sunshine. 264. A further and more effectual provision for restraining the perspiration of leaves within due limits is found in the Epidermis, or skin, that invests the leaf, as it does the whole surface of the vege- table (69), and which is so readily detached from the succulent leaves of such plants as the Stonecrop and the Live-for-ever (Sedum) of the gardens. The epidermis is composed of small cells belonging to the outermost layer of cellular tissue, with the pretty thick-sided walls very strongly coherent, so as to form a firm membrane. Its cells contain no chlorophyll. In ordinary herbs that allow of ready evaporation, this membrane is made up of a single layer of cells ; as in the Lily, Fig. 221, and the Balsam, Fig. 220. It is composed of two layers in eases where one might prove insufficient; and in the Oleander, besides the provision against too copious evaporation, already described (263), the epidermis consists of three com- pact layers of very thick-sided cells (Fig. 222). It is generally thick, or hard and impermeable, in the firm leaves of the Pitto- sporum, Laurustinus, and other plants, which wiU tlirive, for this very reason, where those of more delicate foliage are liable to per- ish, in the dry atmosphere of our rooms in 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 Gray, Asa, 1810-1888. New York [etc. ] Ivison, Blakeman, Taylor & Co.
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