Page:The Journal of Indian Botany.djvu/98

 pericycle forming a loose ring of bast fibres. Oxalate of lime not occurring in any form.

Structure of the Leaf:—Epidermis in P. erioptera consists of tabular cells with outer and inner walls arched convexly outwards and inwards respectively. Outer walls are thickened; lateral walls are thin and straight.

Stomata occur on both the surfaces of the leaf. The guard-cells are surrounded by ordinary epidermal cells and are situated in the plane of the surrounding cells (figs. 38, 41). The front cavity is arched over by outer horns of the guard-cells, which are quite prominent and come close together. The front cavity is placed in a depression formed by the outer thickened walls of the epidermal cells. Stomata on the axis (fig. 41) of both the species have the same characters as those on the leaf of P. erioptera. The mesophyll is composed of the palisade tissue on the upper side and of arm-palisade tissue on the lower. There are numerous lysigenously formed cavities in the arm-palisade tissue (fig. 38 L.C.); they may occasionally serve for storing water.

Oxalate of lime occurs in the form of clustered crystals near the veins of the leaves and in the assimilatory tissue of the axis of P. erioptera (figs. 38, 39). Besides the clustered crystals, there are elongated compact bundles of diamond shaped bodies, in the palisade tissue of the leaf; these bundles are comb-like at their ends on account of the projecting pointed ends of the diamond shaped bodies. As regards composition of these bodies, I cannot say anything. Oxalate of lime is not found in any form in P. irregularis.

Veins are few and are embedded; they are enclosed in bundle-sheaths of thin-walled colourless cells.

Hairy covering on the leaf and axis in both the species consists of unicellular thin-walled clothing hairs, either straight or hooked, and distinguished by knob-like thickenings on their walls. Glandular hairs are not found.

Structure of the Axis:—Epidermis is two-layered in P. erioptera while it is single layered in P. irregularis. Epidermal cells are tabular with outer-walls greatly thickened. Outer walls are convexly arched outwards in P. irregularis. Cuticle is thick, especially so in P. erioptera. Lateral walls are straight. The primary cortex functions as the assimilatory tissue and is composed of chlorophyll containing parenchyma in P. irregularis and of palisade tissue in P. erioptera. Groups of stone-cells occur in the ribs.

The pericycle is composed of a more or less continuous ring of bast-fibres, which are thickened, straitified and have a narrow lumen in P. erioptera. The ring is of uniform breadth in P. erioptera, while