PLANTS OF THE INDIAN DESEKT. 191 



axis. The pifch is composed of thick- walled cells and is characterised 

 by sieve-sclereids. 



CELASTRACEAE. 



Gymnospuria montana Benth.—'Figs. 86, 87. Upper epider- 

 mis locally two-layered. Lower epidermis formed of vertically 

 elongated and papillose cells. Mesophyll consisting of palisade tissue 

 on the adaxial side and of arm-palisade tissue on the abaxial side. 

 Internal glands consisting of cells with tanniniferous contents in the 

 loaf and axis. Oxalate of lime not occurring in any form. Veins 

 vertically transcurrent and enclosed in bundle-sheaths. Hairy cover- 

 ing absent. Pericycle composed of groups of stone-cells. Cork sub- 

 epidermal. Wood prosenchyma formed of cells with thick walls and 

 small lumina. Medullary rays 1-2 seriate. Pith heterogenous. 



Structure of the Leaf. — The upper epidermis consists of tabular 

 cells, with inner walls convexly arched inwards ; it is locally two- 

 layered by division walls which may be thin or thickened and which 

 are parallel to the surface of the leaf. The lower epidermis consists 

 of polygonal cells which are greatly elongated vertically and are 

 drawn out into papillae (fig. 86). Outer walls are thickened ; inner 

 walls are also thickened except in some cases, when the upper epider- 

 mal cells are divided by walls parallel to the surface. The lateral 

 walls are thin and straight. The tendency to form a two-layered 

 epidermis as well as the palisade-like elongation of the epidermal cells 

 are adaptations to protect the palisade tissue against insolation as 

 well as to check transpiration by depressing the stomata. 



The stomata are numerous only on the lower surface and are 

 surrounded by ordinary epidermal cells. The guard-cells are depress- 

 ed and the front cavity is placed in a deep depression formed by the 

 palisade-like surrounding cells. 



The mesophyll is composed of palisade tissue on the adaxial side 

 and of arm-palisade tissue on the abaxial side. In the mesophyll 

 there are numerous cells with tanniniferous contents. Secretory cells 

 with tanniniferous contents are abundantly found in all tissues of the 

 axis, Tanniniferous contents are found in cortical parenchyma, in 

 cells separating the groups of stone-cells of the pericycle, in numerous 

 cells in the soft bast and in the medullary ray cells which are 

 opposed to the glandular cells between the pericyclic stone-cell groups. 

 Oxalate of lime does not occur in any form in the leaf or axis. 



The veins are enclosed in green bundle-sheaths and are vertically 

 transcurrent above and below by colourless thick-walled parenchyma. 

 There are small groups of stone-cells on the lower side of the phloem 

 of larger veins, thus protecting it. 



1766-25 



