Page:The Journal of Indian Botany.djvu/493

 with green bundle-sheaths. Larger veins vertically transcurrent. Clothing hairs two-armed. Glandular hairs absent. Fericycle formed of isolated stone-cells and of very small stone-cell groups. Assimilatory tissue in the axis formed of chlorenchyma. Wood composite. Pith of thick- walled cells.

Convolvulus microphyllus Sieb — Figs. 228, 229. Guard-cells elevated. Front cavity placed in a depression formed by outer thickened epidermal walls. Mesophyll isobilateral. Veins embedded and provided with green bundle-sheaths. Internal glands and oxalate of lime absent. Terminal cell of the clothing hairs seated obliquely on the stalk cell. External glands spherical on the leaf and club- shaped on the axis. Pericycle formed of thin long groups of stone-cells. Aasimilatory tissue in the axis formed of palisade cells. Wood composite and narrowed on two opposite sides. Pith of thin-walled cells.

Convolvulus glomeratUS Chois.— Fig. 230. Guard-cells ele- vated. Front cavity on a level with the surface. Mesophyll of palisade tissue on the adaxial side and of arm-palisade tissue on the abaxial side. Secretory cells with surrounding subsidiary cells present. Oxalate of lime absent. Veins embedded and without bundle-sheaths. Clothing hairs with terminal cell vertically placed on the stalk cell. External glands club shaped. Assimilatory tissue in the axis parenchymatous. Pericycle of closely placed thin long groups of stone-cells. Wood composite and narrowed on two opposite sides. Pith of thin- walled cells.

Ipomoea sindica Stapf.— Figs. 231, 232, 233, 234, 235. Guard- cells elevated. Front cavity on a level with the surface. Mesophyll of palisade tissue on the adaxial side and of arm-palisade tissue on the abaxial side. Internal glands absent in the leaf and found in the axis in the form of secretory cells with tanniniferous contents. Oxalate of lime absent. Terminal cell of clothing hairs superficially knobbed and seated vertically on the stalk-cell which is placed on an epidermal cell in the leaf and on a multicellular pedestal on the axis. External glands horizontal. Assimilatory tissue in the axis parenchymatous. Wood composite and narrowed on two opposite sides. Pericycle forming a composite ring of stone-cells. Pith of thin-walled cells with granular contents.

Structure of the Leaf: — The epidermis consists of tabular cells with the outer walls thickened and convexly arched outwards ; inner walls are also thickened. The lateral walls are thin and straight. The cuticle is thin and striated.

The stomata are developed equally on both the surfaces of isobilateral leaves ; they are more numerous on the lower surface of