Page:The Journal of Indian Botany.djvu/288

 The pericycle forms a more or less composite ring of stone-cells. Small groups of stone-cells occur in the soft bast. The wood is compo- site. Vessels are large and are arranged in incomplete rows. Inter- fascicular wood prosenchyma is extensive and is composed of small thick-walled cells with small lumina. The medullary rays are unis- eriate. Wood parenchyma is little developed.

Pith is composed of small cells with thickened and lignified walls.

Neurada procumbens L. — Figs. 122, 123, 124.— Epidermal cells tabular with outer and inner walls thickened and convexly arched outwards and inwards respectively. Stomata found on both the surfaces and accompanied by ordinary epidermal cells. Hairs uncellular and wooly. External glands absent. Mesophyll composed wholly of short palisade cells. Internal secretory cells with mucila- ginous membrances on all sides and occurring near the veins in the leaf, and in collenchyma, cortical parenchyma, medullary rays and pith of the axis. Epidermal cells with tanniniferous contents. Leaves many ribbed. Smaller veins embedded. Larger veins vertically trans- current by collenchyma. Epidermal cells of the axis with outer- walls papillose. Medullary rays broad. Interfascicular wood prosen- chyma absent. Pith composed of thin-walled cells. Pith cells with mucilaginous walls towards the periphery.

Structure of the Leaf: — The epidermis consists of tabular cells with outer and inner walls convexly arched outwards and inwards respectively. Lateral walls are thin and straight. Epidermal cells hold tanniniferous contents. The stomata are more numerous on the lower surface and are surrounded by ordinary epidermal cells. The guard-cells are situated in the plane of surrounding cells and the front cavity is placed in a depression formed by the outer thickened epidermal walls fig. 123. The stomata on the axis are similar to those on the leaf.

The mesophyll is wholly composed of short palisade cells fig. 122. Internal secretory organs are represented by cells with mucilaginous membranes on all sides and by epidermal cells of the leaf with tanniniferous contents. Cells with mucilaginous membranes occur near the veins, at the inner margin of cortex, in the medullary rays and in the pith tissue towards the periphery. Tanniniferous contents in the epidermal cells of the leaf give an acrid taste to foliage leaves and prevent them from being easily devoured by animals.

Oxalate of lime is found in the form of numerous small clustered crystals near the veins of the leaf and in collenchyma and soft bast of the axis. The leaves are many ribbed, the ribs being prominent