PLANTS OF THE INDIAN DESERT. 7i 



ferenfe portions of the axis which are not equally affected by the sun 

 and wind. The pith consists of thin-walled cells or of cells with 

 thickened and lignified walls. 



SOLANAGEAE. 



SolaD um incanum L. — Figs. 241, 242, 243, 244. Mesophyll 

 bifacial. Oxalate of lime found in the form of crystal sand in meso- 

 phyll, cortex, soft-bast, intraxylary phloem and pith. Clothing hairs 

 tufted. Epidermis one layered. Cork subepidermal. Collenchyma 

 developed below cork. Pericycle forming a loose ring of bast fibres. 

 Vessels arranged in bundles connected by strands of interfascicular 

 wood prosenchyma. 



Solanum albicaule Kotsc — Figs. 236, 237, 238. Mesophyll 

 isobilateral. Oxalate of lime found in the form of crystal sand in 

 mesophyll and pith. Clothing hairs tufted and uniseriate trichomes. 

 Epidermis of the axis three layered. Collenchyma subepidermal. 

 Vessels few and uniformly distributed in the wood-ring. Intraxylary 

 phloem present. 



Lycium barbarum L.— Fig. 239. Mesophyll isobilateral. Oxal- 

 ate of lime found in the form of crystal sand in mesophyll of the leaf 

 and epidermis s soft bast and pith of the axis. Clothing hairs absent. 

 Epidermis of the axis one-layered and with outer walls thickened and 

 muriculate. Sclerenchymatous pericycle not developed. Cork sube- 

 pidermal and characterised by isolated stone-cells. Vessels few and 

 uniformly distributed in the wood-ring. Intraxylary phloem present- 



Structure of the Leaf : — The epidermal cells are tabular with the 

 outer walls thickened and convexly arched outwards. The lateral 

 walls are thin and undulated. The outer walls in L. barbarum (fig. 

 239) are muriculate. The upper epidermal cells are mostly filled with 

 crystal sand. 



The stomata are equally numerous on both the surfaces of isobi- 

 lateral leaves, while they are more numerous on the lower surface of 

 bifacial leaves. The front cavity is placed in a depression formed by 

 outer thickened epidermal walls. The guard-cells are accompanied by 

 ordinary epidermal cells. 



The mesophyll is isobilateral in S. albicaule and L. barbarum and 

 is bifacial in S. incanum. Some of the palisade cells contain crystal 

 sand. 



Oxalate of lime occurs in the form of crystal sand in all 

 members. Cells filled with crystal sand are found abundantly in the 

 mesophyll of the leaf and in the epidermis of the axis of L. barbarum , 



