. An introduction to the structure and reproduction of plants. Plant anatomy; Plants. 38 MUCILAGE AND GUM The walls of mature cells often undergo chemical changes other than hgnification, some of which [ the change affecting the cells of the cork, p. 136) will be described later, but a few special cases may conclude the present chapter. In a number of plants the thickening of the walls of certain cells takes the form of layers of mucilage, whose exact chemical constitution is not known. These, in the dry condition, are hard and horny, but in the presence of moisture they soften and swell u
. An introduction to the structure and reproduction of plants. Plant anatomy; Plants. 38 MUCILAGE AND GUM The walls of mature cells often undergo chemical changes other than hgnification, some of which [ the change affecting the cells of the cork, p. 136) will be described later, but a few special cases may conclude the present chapter. In a number of plants the thickening of the walls of certain cells takes the form of layers of mucilage, whose exact chemical constitution is not known. These, in the dry condition, are hard and horny, but in the presence of moisture they soften and swell up con- siderably. Indeed, such mucilaginous walls possess a remarkable. Fig. ig.—Transverse section of the leaf of a Nettle (Urlica) showing a cystolith (C ). Ch., Cuticle ; £/>., epidermis ; A, hair; Pa., palisade tissue : Sp., spongy parenchyma. power of absorbing and holding water, and arc consequently particularly prevalent in plants characteristic of dry situations. The slimy character of many Seaweeds [ the common Bladder- wrack) is due to the mucilaginous nature of nearly all the cell- walls, and here the change in bulk, as between the dry and wet condition, is especially evident. Mucilaginous walls stain deeply and rapidly with aniline blue. The gums formed by certain plants arc probably very similar chemically to the mucilages, and, Uke thenr, appear, in many cases at least, to arise as a result of chemical alteration of the. 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 Fritsch, Felix Eugene, 1879-; Salisbury, E. J. (Edward James), Sir, b. 1886. London, G. Bell and sons ltd.
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