196 THE JOUENAL OF INDIAN BOTANY. 



The pith consists of thin- walled cells. 



MORINGASEAE 



Moringa pterygosperma Gaert.-* Figs. 96, 97. Leaf. Water- 

 storing cells vertically elongated, conspicuous and numerous in upper 

 epidermis. Mesophyll formed of palisade tissue on the adaxial side 

 and of spongy tissue on the abaxial side. Myrosin cells in the form 

 of palisade-like cells and confined to the palisade tissue. Oxalate of 

 lime absent. Veins enclosed in bundle-sheaths. Short unicellular 

 clothing hairs occurring on both surfaces. 



Moringa concanensis Nimmo: — Eig, 98. Leaf. Water-storing 

 cells in upper epidermis few and formed of a little enlarged epider- 

 mal cells. Lower epidermal cells with outer walls forming large 

 papillae. Mesophyll composed of rows of palisade cells separated by 

 myrosin cells on the adaxial side, and of armpalisade tissue on the 

 abaxial side. Myrosin cells occurring between the rows of palisade 

 cells as well as on the inner side of arm-palisade tissue. Clustered 

 crystals of oxalate of lime numerous near veins and below lower 

 epidermis. Veins not enclosed in bundle-sheaths but strengthened 

 by arcs of stone-cells on their lower side. Hairs absent. 



Structure of the Leaf : — The epidermis differs in structure on the 

 two surfaces. The epidermal cells on the upper surface are tabular 

 with outer and inner walls equally thickened and convexly arched 

 outwards and inwards respectively. There are large water-storing 

 cells, which are numerous and conspicuous in M. pterygosperma (fig. 

 96) intercalated amongst the ordinary epidermal cells, (figs. 96, 98). 

 The epidermal cells on the lower surface are much smaller than those 

 on the upper surface. The outer and inner walls are equally thickened 

 and the latter are curved convexly outwards in the form of papillae 

 which are very large in M. concanensis (fig. 96). Lateral walls are 

 thin and straight. 



Stomata occur only on the lower surface and are surrounded by 

 ordinary epidermal cells. Guard-cells are situated quite below the 

 plane of the epidermal cells. The front cavity is therefore placed in 

 a pit as deep as the height of the epidermal cells ; air in these pits 

 remains moist and transpiration is thus greatly diminished. This kind 

 of contrivance is necessary in leaflets of species of Moringa which are 

 not protected by a dense covering of hairs and which, on the other 

 hand, are greatly shaken by wind, thus accelerating transpiration. 



The hairy covering consists of a few short, thick-walled unicellu- 

 lar clothing hairs found on both the surfaces of M. pterygosperma 

 (fig. 96) ; it does not occur in M. concanensis. External glands are 

 absent. 



