Clothing as well as glandular hairs do not occur on the leaf and axis. The absence of a hairy covering is compensated for partly by the palisade-like elongated epidermal cells and partly by the two- layered epidermis.
Structure of the Axis.—The epidermis consists of small tabular cells with outer walls thickened. The cortex is composed on its outer side of an extensive cork tissue and on its inner side of glandular tissue already described (fig. 87).
The pericycle is composed of closely placed large groups of stone-cells separated by secretory cells with tanniniferous contents. The wood is composite (fig. 87). Vessels are fairly large and numerous. Interfascicular wood prosenchyma is composed of thin-walled cells with small lumina. The medullary rays are 1-2 seriate and are numerous, some of their cells holding tanniniferous contents.
The pith is heterogenous and is composed of groups of large elongated cells surrounding small cells (fig. 87).
RHAMNEAE.
Zizyphus jlljuba Lam. — Fig 88. Epidermis composed of hori- zontally tabular cells. Upper epidermis of the mid-rib grooved. Uniseriate trichomes more numerous on the lower surface. Secretory cavities not found in cortex. Pericycle formed of stone-cells. Long thin groups of stone-cells present in soft bast.
Zizyphus trinervia Roxb— Figs. 89, 90. Epidermis of the leaf composed of cubical or vertically tabular cells. Upper epidermis of the mid-rib not grooved. Uniseriate trichomes absent on the upper surface. Secretory cavities numerous in the cortex. Long thin groups of stone-cells found in soft bast. Pericycle formed of bast fibres.
Zizyphus rotundifolia Lam.—Figs. 91, 92. Epidermis of the leaf formed of cubical and vertically tabular cells. Upper epidermis of the mid-rib grooved. Uniseriate trichomes more numerous on the lower epidermis. Secretory cavities wanting in cortex. Stone-cells absent in soft bast. Pericycle formed of bast fibres.
Zizyphus truncata Blatt. and Hall. —Figs. 93, 94. Upper epidermis consisting of cubical and vertically tabular cells. Upper epidermis of the mid-rib not grooved. Uniseriate trichomes absent on the upper surface. Secretory cavities occurring in cortex. Stone-cells wanting in soft bast. Pericycle formed of bast fibres.
Structure of the Leaf:—The epidermis of the two surfaces differ in structure. The upper surface is smooth while the lower one is characterised by alternate ridges and furrows. The epidermal cells of the upper surface are larger and cubical or vertically tabular in all members (figs. 91, 93,) except Z. jiijuba where they are mostly
