. The natural history of plants, their forms, growth, reproduction, and distribution;. Botany. ABSORPTION OF RAIN AND DEW BY THE FOLIAGE-LEAVES. 229 tion of water is not very considerable. But it often happens that the uppermost cells of a septate hair are developed into absorption-cells. The terminal cell is then usually spherical or ellipsoidal and larger than the rest, or else this cell is divided into two, four, or a greater number of cells, which together form a little head, whilst the lower cells constitute a stalk supporting it (see fig. 533 and 53 4). In botanical terminology structure
. The natural history of plants, their forms, growth, reproduction, and distribution;. Botany. ABSORPTION OF RAIN AND DEW BY THE FOLIAGE-LEAVES. 229 tion of water is not very considerable. But it often happens that the uppermost cells of a septate hair are developed into absorption-cells. The terminal cell is then usually spherical or ellipsoidal and larger than the rest, or else this cell is divided into two, four, or a greater number of cells, which together form a little head, whilst the lower cells constitute a stalk supporting it (see fig. 533 and 53 4). In botanical terminology structures of this kind are named capitate or glandular hairs. The protoplasm in the cells of the head is, for the most part, of a dark colour, and the. Fig. 53.—1 Cauline hairs of Stellaria media; x 110. 2 Lowest cells of the same hairs; x 200. 8 Capitate hairs of Centaurea Balsamita; X150. * Capitate hairs of Pelargonium lividum; xl50. cell-membranes are readily permeable by water, which is attracted with great energy by the cell-contents. The cell-membrane is often very thick, it is true, but as soon as water comes into contact with it the outer layer is discarded, the inner layers swell up and the water passes through these swollen layers into the interior of the cell. This happens, for instance, in many pelargoniums and geraniums, wherein the capitate cells go through a process of excoriation on every occasion of the imbibition of water (see fig. 53*). In other plants the walls of the capitate cells are everywhere thin, and not only do the cell-contents consist of a viscid gum- like mass, but the external surface of the wall is also covered by a layer of viscid excretion. In many cases the viscid matter excreted by the glands spreads over the entire surface of the leaf, so that the latter feels sticky and looks as if it were. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of th
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