. Text-book of botany, morphological and physiological. Botany. 66 MORPHOLOGY OF THE CELL. usually more or less completely fill up the cells, which are mostly elongated. Needles of this kind are formed also in great quantities when the leaves of many woody plants change their colour and lose water by evaporation in the autumn, although absent during the period of growth. Where the crystals lie in the cavity of the cell—and this is usually the case with Angiosperms—they are commonly, perhaps always, coated by a thin membrane, which remains after solution of the calcium oxalate, and must probabl
. Text-book of botany, morphological and physiological. Botany. 66 MORPHOLOGY OF THE CELL. usually more or less completely fill up the cells, which are mostly elongated. Needles of this kind are formed also in great quantities when the leaves of many woody plants change their colour and lose water by evaporation in the autumn, although absent during the period of growth. Where the crystals lie in the cavity of the cell—and this is usually the case with Angiosperms—they are commonly, perhaps always, coated by a thin membrane, which remains after solution of the calcium oxalate, and must probably be con- sidered as a coating of protoplasm. This is also the case, according to Payen, even with raphides, and, according to the accurate observations of others, also in the larger single crystals and clusters. In Angiosperms calcium oxalate occurs apparently only rarely deposited in the substance of the cell-wall; Solms-Laubach (/. c.) cites different species of Mesem- bryanthemum (M. rhombeum, tigrinum lacerum, slramzneum, Lemanni) and Sempervivum calcareum, in which fine granules or (in the last case) larger angular fragments of crystalline calcium oxalate are scattered through certain layers of the outer wall of the epidermal cells of leaves. Among Mono- cotyledons, Pfeffer has observed well-developed crystals in the thickened cuticle, and in cells which lie deeper in the tissue, of Draccena reflexa, arborea, Draco, and umbra- culifera. The occurrence of crystals of calcium oxalate in the sub- stance of the cell-walls is, on the other hand, according to Solms-Laubach, of common occurrence in Gymnosperms. They generally consist of numerous small granules of un- recognisable shape; not unfrequently, however, they are well-developed crystals. In the bast-tissue of all parts of the stem deposits of this kind are found in the Cupressinese, Podocarpus} Taxus, Cephalolaxus, and Ephedra; they are absent, on the other hand, from Phyllocladus trichomanoides, Salisburia adianiif
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Keywords: ., bookcentury1800, bookdecade1880, booksubjectbotany, bookyear1882
