Page:The Journal of Indian Botany.djvu/226

 lular and with muriculate walls. Glandular hairs formed of a short uniseriate stalk and of an obconical unicellular head. Oxalate of lime found in the form of clustered crystals. Leaf many-ribbed. Veins of the ribs vertically transcurrent. Smaller veins embedded.

Structure of the Leaf.—The epidermal cells are polygonal with outer walls papillose much more so on the lower surface. The outer and inner walls are equally thickened. Inner walls are convexly arched inwards, thus coming into close contact with the assimilatory tissue. The lateral walls are thin and undulated. The stomata are more numerous on the lower surface and are accompanied by ordinary epidermal cells. Guard-cells are situated in the plane of the outer epidermal walls ; and the front cavity Ms on a level with the surface.

The hairy covering consists of clothing and glandular hairs the former are more numerous on the lower surface and the latter more numerous on the upper. The clothing hairs are unicellular and have muriculate walls; the basal portion is conical and is inserted between the epidermal cells (figs. 79, 81). Glandular hairs are formed of a short uriseriate stalk and of an obconical head (figs. 79, 80).

The mesophyll is composed of a layer of very long palisade cells on the adaxial side and of an arm-palisade tissue on the abaxial side. The elongated form of the palisade cells affords protection, against intense light, to the chlorophyll grains. The greatly elongated palisade cells, the development of arm-palisade tissue and the thickening of the outer and inner epidermal walls are distinct proofs of xerophytic characters developed by the plant. Internal secretory organs are not found in the leaf or axis. Oxalate of lime occurs in the form of clustered crystals near the veins.

The leaves are many-ribbed. The ribs are prominent below and grooved above. The veins of the ribs are vertically transcurrent above by colourless parenchyma and below by collenchyma. Smaller veins are embedded. Bundle-sheaths are not found round the veins

Balanites Roxburghii Planch.— Figs. 82. 83, 84. Epidermal cells of the leaf and axis tabular. Mesophyill-bifacial. Stomata depressed with guard-cells below the plane of the surrounding cells. Internal glands absent. Oxalate of lime found in the form of solitary and clustered crystals in the leaf and axis. Veins embedded and enclosed in bundle sheaths. Groups of water-storing tracheids occurring at intervals between the veins. Clothing hairs present in the form of short thick-walled unicellular trichomes. Glandular hairs absent. Assimilatory tissue in the axis formed of chlorenchyma. Cortical