Page:The Journal of Indian Botany.djvu/281

 Veins vertically transcurrent by sclerenchyma and provided with bundle-sheaths. Tannin sacs absent. Clothing hairs hooked. External glands formed of a stalk-cell and of a globose head. Assimilatory tissue in the axis chlorenchyrnatous. Pericycle formed of stone-cells. Medullary rays 1-2 seriate. Pith formed of thin-walled cells.

Phaseolus trilobus Ait.— Fig. 112. Epidermal cells tabular with inner walls gelatinised. Mesophyll bifacial. Veins vertically transcurrent by collenchyma. Bundle-sheaths absent. Tannin sacs in the palisade tissue. Clothing hairs in the form of uniseriate trichomes with muriculate walls. External glands culb-shaped. Assi- milatory tissue in the axis chlorenchmatous. Pericycle formed of bast fibres. Medullary rays 1-2 seriate. Pith formed of thin-walled cells.

Rhynchosia arenaria Blatt. and Hall— Figs. 116, 117. Epi- dermal cells tabular. Mesophyll bifacial. Veins vertically transcurrent by sclerenchyma and provided with bundle-sheaths. Tannin sacs found in the middle of the mesophyll and in soft bast. Clothing hairs in the form of uniseriate trichomes with muriculate walls. External glands consisting of an uniseriate stalk and of a spherial head. Assi- milatory tissue in the axis chlorenchyrnatous. Pericycle formed of stone-cells. Medullary rays 2-3 seriate. Pith formed of thin-walled cells.

Rhyncosia rhombifolia Blatt. and Hall—Figs. 113, 114, 115.

Epidermal cells tabular. Mesophyll bifacial. Veins vertically transcurrent by sclerenchyma and not provided with bundle-sheaths. Tannin sacs found in the middle of the mesophyll and in soft bast. Clothing hairs in the form of uniseriate trichomes with muriculate walls. External glands formed of an uniseriate stalk and of a spheri- cal head. Assimliatory tissue-in*the axis chlorenchyrnatous. Pericycle formed of stone-cells. Medullary-rays 2-3 seriate. Pith formed of thick-walled cells.

Structure of the Leaf: — Epidermal cells may be tabular with straight lateral walls, or may be polygonal with lateral walls undulated, as in species of Crotalaria fig, 100 and Heylandla latebrosa fig. 99. Outer walls are thickened and cuticularised ; inner and lateral walls are thin. There are large thin-walled water-storing cells with outer and inner walls convexly arched outwards and inwards respectively, intercalated amongst the ordinary epidermal cells in G. Burhia fig. 100 and H. latebrosa fig. 99. The toothed condition of the outer walls in A. vaginalis may be the result of the arrest of parenchyma owing to the deficiency of water. Papillose differentiation of the outer walls js rare, Inner walls in P. trilobus are gelatinised,