. How crops grow. A treatise on the chemical composition, structure, and life of the plant, for all students of agriculture ... Agricultural chemistry; Growth (Plants). THE VEGETATITE ORGANS OP PLANTS. 285 Below the upper epidermis, there often occur one or more layers of oblong cells, whose sides are in close eon- tact, and which are arranged endwise, with reference to the flat of the leaf Below these, down to the lower epi- dermis, for one-half to three-quarters of the thickness of the leaf, the cells are commonly spherical or irregular in figure and arrangement, and more loosely disposed, w
. How crops grow. A treatise on the chemical composition, structure, and life of the plant, for all students of agriculture ... Agricultural chemistry; Growth (Plants). THE VEGETATITE ORGANS OP PLANTS. 285 Below the upper epidermis, there often occur one or more layers of oblong cells, whose sides are in close eon- tact, and which are arranged endwise, with reference to the flat of the leaf Below these, down to the lower epi- dermis, for one-half to three-quarters of the thickness of the leaf, the cells are commonly spherical or irregular in figure and arrangement, and more loosely disposed, with numerous and large interspaces. The interspaces among the leaf-cells are occupied with air, Avhich is also, in most cases, the only con- tent of the epidermal cells. The active cells of the leaf contain some or all of the various proximate principles which have been already noticed, and in addition the coloring matter of vegetation, —the so-called chlorophyll^ or leaf-green, p. 109. Under the microscope, this sub- stance is commonly seen in the form of minute grains attached to the walls of the cells, as in fig. 56, or coating starch granules, or else floating free in the cell-sap. The structure of the veins or ribs of the leaf is similar to that of the vascular bundles or fibers of the stem, of wliich they are branches. At «, fig. 56, is seen the cross section of a vein in the bean-leaf. The epidermis^ while often smooth, is frequently beset with hairs or glands, as seen in the figure. These are va- riously shaped cells, sometimes empty, sometimes, as in the nettle, filled with an acid liquid. Their office is httle understood. Leaf-Pores.—The epidermis is further provided with a vast number of curious "breathing pores," ors«o?wa«a,by means of which the intercellular spaces in the interior of the leaf may be brought into direct communication with the outer atmosphere. Each of these stomata consists. Digitized by Microsoft®. Please note that these images ar
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