ASCLEPIADACEAE.
Glossonema varians Benth. -Leaves fleshly. Epidermal cells with outer walls thickened. Guard-cells elevated. Mesophyll formed of palisade tissue on the adaxial side and of arm-palisade on the abaxial side. Cortical parenchyma extensive and formed of thin- walled colourless cells. Pericycle composed of rhomboidal groups of bast fibres with large lumina. Medullary rays uniseriate. Pith consisting of thin-walled cells with brownish contents.
Calotropis procera Br.— Figs. 197, 198 {Leaf only). Leaves fleshy. Epidermal cells with outer walls greatly thickened. Cuticle very thick. Guard-cells on the adaxial side situated quite below the plane of epidermal cells ; those on the abaxial side elevated. Meso- phyll consisting of extensive palisade tissue on the upper side and of extensive loose arm-palisade tissue on the lower. Clothing hairs in the form of very shorfe uniseriate trichomes.
Pentatropis cynanchoides Br. — Leaves fleshly. Epidermal cells with outer walls thickened. Guard-cells elevated. Mesophyll wholly of arm-palisade tissue. Epidermis of the axis two-layered. Oxalate of lime in the form of clustered crystals in cortex and soft bast. Internal secretory cells with tanniniferous contents found in cortex and pith. Pericycle formed of long thin groups of stone-cells. Medullary rays uniseriate. Pith consisting of thin-walled cells.
Sarcostemma brevistigma Wt.— Fig. 199. Leafless. Epi- dermal cells longer than broad. Guard-cells quite below the plane of epidermal cells. Cortical parenchyma extensive and aqueous. Peri- cycle formed of rhomboidal groups of stone-cells. Medullary rays uniseriate. Pith consisting of thin-walled cells with granular contents.
Leptadenia spariium Wt. — Fig. 200. Almost leafless. Stomota in depressions formed by thickened outer epidermal walls. Mesophyll isobilateral. Clothing hairs in the form uniseriate trichomes with vermcose walls. Epidermis of the axis three-layered. Internal secretory cells with tanniniferous contents. Pericycle of rhomboidal groups of stone-cells. Vessels large on the outer side and small on the inner side. Medullary rays 1-2 seriate. Pith consisting of thin-walled cells.
Structure of the Leaf. — -The epidermis is composed of small polygonal cells in all members except in G. procera and P. cynanchoides where the epidermal cells are tabular. The outer walls are thickened and convexly arched outwards. The cuticle in C. procera is con- siderably thickened (fig. 197). In G. procera and L. spartiirm it is superficially granulated. The epidermal cells are alike on both the surfaces except in G. variant and P. cynanchoides, where the epider- mal cells on the upper side are much larger than those on the lower.
