. The elements of botany for beginners and for schools. Plants. SECTION 1G.] ANATiiMV OF IS. 143 greeu pulp, ami i> nearly the Bame aa the green layer of the bark. 80 that the Leaf maj properly enough be regarded as a Borl of expansion of the fibrous and green layers of the bark. It has no proper corky layer; but the whole is covered by a transparent skin or epidermis, resembling that of tho stem. 1 tO. The cells of the leaf are of various forms, rarely so compact as to form a eellular tissue, usualU loosely arranged, at least in the lower part, so as to give copious intervening
. The elements of botany for beginners and for schools. Plants. SECTION 1G.] ANATiiMV OF IS. 143 greeu pulp, ami i> nearly the Bame aa the green layer of the bark. 80 that the Leaf maj properly enough be regarded as a Borl of expansion of the fibrous and green layers of the bark. It has no proper corky layer; but the whole is covered by a transparent skin or epidermis, resembling that of tho stem. 1 tO. The cells of the leaf are of various forms, rarely so compact as to form a eellular tissue, usualU loosely arranged, at least in the lower part, so as to give copious intervening spaces or air passages, communi- cating throughout the whole interior (Fig. 443, 4S3). The green color is given by the chlorophyll (417), seen through the very transparent walls of the cells and through the translucent epidermis of the leaf. 441. In ordinary leaves, having an upper and under surface, the green cells form two distinct strata, of different arrangement. Those of the upper stratum arc oblong or cylindrical, and stand endwise to the surface of the leaf, usually close together, leaving hardly any vacant spaces; those of the lower are commonly irregular in shape, most of them with their longer diameter parallel to the face of the leaf, and are very loosely ar- ranged, leaving many and wide air-chambers. The green color of the lower is therefore diluted, and paler than that of the upper face of the leaf. The upper part of the leaf is so constructed as to bear the direct action. of the sunshine ; the lower so as to afford freer circulation of air, and to facilitate transpiration. It communicates more directly than the upper with the external air by means of StomaUt. 442. The Epidermis or skin of leaves and all young shoots is best seen in the foliage. It may readily lie .stripped off from the surface of a Lily-leaf, and still more so fn lore fleshy and soft leaves, such as those Pio. 188. Magnified section of a leaf f White Lily, to exhibit the cellular Btructare, both
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Keywords: ., bookcentury1800, bookdecade1880, booksubjectplants, bookyear1887
