. Biology. Biology. HISTOLOGY OF THE FERN 113 longer than the vertical; the two sides, furthermore, show some- what flattened ledge-like surfaces which are turned upward, a differentiation offering more resistance to up-rooting than would be the case if the sides were smoothly rounded. The cross section also shows various cellular differentiations. On the outside is a layer of cells termed the cortex, consisting of an outer black and lifeless layer to which the name epidermis is given, while below this is a layer of hardened, almost wood-like,. FIG. 44.—Transverse section of a vascular bundle
. Biology. Biology. HISTOLOGY OF THE FERN 113 longer than the vertical; the two sides, furthermore, show some- what flattened ledge-like surfaces which are turned upward, a differentiation offering more resistance to up-rooting than would be the case if the sides were smoothly rounded. The cross section also shows various cellular differentiations. On the outside is a layer of cells termed the cortex, consisting of an outer black and lifeless layer to which the name epidermis is given, while below this is a layer of hardened, almost wood-like,. FIG. 44.—Transverse section of a vascular bundle surrounded by funda- mental tissue. The conducting system of the plant. (From Sedgwick and Wilson.) cells forming the bulk of the cortex. These cortex cells are hardened by the lignincation of the protoplasmic structures, this lignin forming the chief element in the composition of the still more hardened wood tissues within the rhizome. Within the cortex is a mass of living parenchyma cells with soft and un- differentiated protoplasm, well supplied with starch, and form- ing the bulk of the mass of the rhizome. Scattered among these parenchyma cells are two large masses and other smaller patches of dark brown material formed by the lignincation of the funda-. 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 Calkins, Gary N. (Gary Nathan), b. 1869. New York, H. Holt and company
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