. Botany, an elementary text for schools. Botany. 254 TISSUES duets and vessels ; the endodermis remains as endodermis; periblem becomes the cortex of parenchyma; the derma- togen becomes the epidermis of the root. 411. EPIDERMAL TISSUE.—This is a special modification of parenchyma, comprising the thin layers on the exterior of leaves and stems. The cells are often tabular or plate- like in form, as in the epidermis of leaves (Fig. 115); and their outer surface bears a layer of cuticle, a protec- tive substance which is insoluble even in sulfuric acid. They do not bear chlorophyll and often co
. Botany, an elementary text for schools. Botany. 254 TISSUES duets and vessels ; the endodermis remains as endodermis; periblem becomes the cortex of parenchyma; the derma- togen becomes the epidermis of the root. 411. EPIDERMAL TISSUE.—This is a special modification of parenchyma, comprising the thin layers on the exterior of leaves and stems. The cells are often tabular or plate- like in form, as in the epidermis of leaves (Fig. 115); and their outer surface bears a layer of cuticle, a protec- tive substance which is insoluble even in sulfuric acid. They do not bear chlorophyll and often contain only cell- sap, with a little protoplasm. Their walls are much thick- ened in some cases, as in Figs. 394 and 414. Hairs and hristles are considered to be modified epidermal tissue. 412. COLLENCHYMATOUS TISSUE.—Tis- sue composed of cells thickened at the angles, not much elongated and not lapping at the ends, is known as collen- chyma (Fig. 396). It is strengthening tissue. Good examples are found in 396. Coiieuciiyma in wild ^^^cli viucs as pumpkiu, cucumbcr and jewel-weed or toixeh-me- gourd. The tissuc is sHghtly clastic uot (impatiens). -j n /. i. j. i • /-i j. and allows or some stretching. Cut a few thin cross-sections of large stems of jewel-weed, and mount in water. Study with high power. 413. SOFT BAST OR SIEVE TISSUE.—In the higher plants is a tissue known as soft bast or sieve tissue (this also forms part of the bundle; 424). It is composed of two types of cells which almost always accompany each other. These are sieve tubes and companion cells (Fig. 397). Both are elongated, thin-walled and blunt at the ends. The sieve tubes are so called because of the sieve-like areas which they bear in various parts. These areas, called sieve plates, are commonly at the ends (as partitions) but may be in the lateral walls. Fig. 397. They serve to connect the cell-cavities with each other, and through. Please note that these images are extracted from scanned page ima
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