PLANTS OF THE INDIAN DESEET. 71 



Numerous large clustered crystals of oxalate of lirne occur in the 

 arm-palisade tissue of the mesophyll. The crystals are wanting in the 

 axis. The veins are embeded and are not provided with bundle- 

 sheaths. 



Both the leaf and the axis are devoid of hairs. The absence of 

 hairs is compensated for by the gelatinisation of the inner walls of the 

 epidermal cells. 



Structure of the Axis : — Epidermis consists mostly of tabular cells 

 with outer walls thickened, muriculate and convexly arched outwards- 

 The inner walls are gelatinised and the lateral walls are straight. 

 The epidermis is distinguished by two common features (l) palisade- 

 like elongation of the epidermal cells in some parts (2) gelatinisation 

 of the inner walls of the epidermal cells which are sometimes 

 characterised by thin dividing walls parallel to the surface beneath 

 which mucilage is found. The epidermis may occasionally serve 

 as a water-storing tissue on account of these two features. 



Cells of the outermost layer of the cortex show collenchymatous 

 differentiation at their outer angles. The cortex is distinguished by 

 the occurrence of cortical vascular bundles in the cortical chlorophyll 

 containing parenchyma. 



Sclerenchymatous pericycle is absent. The structure of the 

 wood is composite. The vessels are small and are arranged almost 

 in numerous complete rows. Interfascicular wood-prosenchyma is 

 little developed. Medullary rays are uniserate and numerous. Small- 

 celled collenchyma occurs at the inner margin of the wood. Soft 

 bast forms a continuous ring. 



The pith consist of thin-walled cells. 



POLYGALACEAE. 



Polygala erioptera .DC —Figs. 38, 39. Leaf and axis.— Numer- 

 ous lysigenous cavities in the lower half of the mesophyll. Clustered 

 crystals occurring near the veins. Compact bundles, comb-like 

 at their ends, of diamond shaped bodies in the palisade-like cells 

 in the upper half of the mesophyll. Epidermis of the axis two- 

 layered. Axis ribbed. Eibs strengthened by stone- cell groups. 

 Assimilatory tissue of the axis formed of palisade tissue. Scler- 

 enchymatous pericycle in the form of groups of thick-walled and 

 stratified bast fibres with small lumen. 



Polygala irregularis Boiss.— Figs. 40, 41. Axis only.— Axis 

 ribbed, groups of stone-cells strengthening the ribs. Epidermis 

 one-layered. Assimilatory tissue composed of chlorenchyma. Aque- 

 ous cells between the groups of bast fibres. Sclerenchymatous 



