Page:The Journal of Indian Botany.djvu/100

 Internal secretory organs are represented by secretory cells with tanniniferous contents in the leaf and axis. In the leaf they are polygonal and lie in the lower half of the mesophyll. In the axis there is a sub-epidermal secretory tissue of one or two layers of tabular cells. Besides, there are numerous outer sclerenchymatous fibres and numerous pith cells with tanniniferous contents. Some of the cells of the medullary-ray-like strands also hold tanniniferous contents. The secretory cells with tanniniferous contents seem to be a characteristic feature of the species.

Oxalate of lime is abundantly found in the form of large clustered crystals near the veins in the leaf. In the axis cells with clustered crystals occur in the outer sclerenchymatous fibres, in the cells of the medullary-ray-like strands and in the pith.

The abundance of tanniniferous substance and of oxalate of lime in the leaf and axis gives an acrid taste to the tissues of the plant and makes it inedible by animals. Abundance of tannin also protects the tissue of the plant from desiccation. The veins are enclosed in green bundle-sheaths. Larger veins occur as usual in the middle of the mesophyll. Besides these, there are smaller veins near the lower epidermis. The vein of the mid-rib is protected above and below by strands of sclerenchyma and is vertically transcurrent below by colourless parenchyma.

The leaf and axis are devoid of clothing and glandular hairs.

Structure of the Axis:—The epidermis consists of small tabular cells with outer and inner walls very greatly thickened. Outer walls are convexly arched outwards. Lateral walls are straight. The cuticle is thick and smooth.

The cortex is characterised by a sub-epidermal tissue of tabular cells with tanniniferous contents. The assimilatory tissue which lies below the secretory tissue is composed of chlorophyll containing parenchyma.

The pericycle is composed of large groups of stone cells situated on the radii of the vascular bundles. Besides these pericyclic groups of stone cells, there is a tissue of sclerenchymatous fibres with larger lumina, continuous with the medullary-ray-like structures between the vascular bundles. There are a few scattered stone cells with walls much thickened and radially striated and with small lumina, on the outer margin of the sclerenchymatous tissue and in the soft bash

The wood is composed of large xylem bundles separated by broad strands of radially elongated thick-walled cells resembling medullary-ray cells. These seem to be continuous with the sclerenchymatous tissue outside the pericyclic groups of stone cells.

There are isolated cases of sclerotic cells with canals, as large