PLANTS OF THE INDIAN DESERT. 73 



cular wood-prosenchyma. This narrowed portion of the wood-ring 

 represent the lower side of the inclined axis where the functional 

 activity is comparatively much less. In addition to the normal zona 

 of soft bast on the outer side of the wood-ring there are groups of 

 intraxilary soft bast on its inner side. Intraxilary soft bast is protec- 

 ted on its inner side by groups stone-cells. The pith consists of thin- 

 walled cells. Some of the pith cells contain crystal sand. 



General Review : — The epidermal cells have their outer walls 

 greatly thickened and cuticularised. The stomata are depressed and 

 occur on both the surfaces ; they are surrounded by ordinary opidermal 

 cells. The mesophyll is bifacial or is isobilateral. Oxalate of limo 

 occurs abundantly in the form of crystal sand in the leaf and axis. 

 The clothing hairs usually consist of a biseriate or multiseriate stalk 

 and of a tuft of ray cells. In addition to the tufted hairs, uniseriate 

 trichomes are found in S. albicaule. Glandular hairs are composed 

 of a short uniseriate stalk and of an ellipsoidal head which is irregul- 

 arly divided. The epidermis of the axis is one-layered or many-layered. 

 The cork is sub-epidermal. The sclerenchymatous pericycle, when 

 present, forms a loose ring of bast fibres. All the members are charac- 

 terised by the occurrence of intraxilary soft bast. The vessels have 

 simple perforations. The interfascicular wood prosenchyma is exten* 

 sive. The medullary rays are uniseriate and numerous. Wood paren- 

 chyma is little developed. Pith consists of thin- walled cells. 



(To be continued.) 



