PLANTS OF THE INDIAN DESEET. 239 



Voins 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, 



