PLANTS OF THE INDIAN DESERT. 163 



terminal cell bent like a hook. The tip of the hair is sharp and 

 solid. External glands are not found. 



Mesophyll is bifacial. Internal secretory organs and oxalate of 

 lime are not found. Veins are embedded and are provided with green 

 bundle-sheaths. 



EUPHORBIACEAE. 



Euphorbia granulata For sk.— Wig. 294. Epidermal cells of 

 the leaf with outer walls greatly papillose. Internal glands absent 

 in the leaf. Internal secretory cells in the axis with tanniniferous 

 contents. Veins provided with bundle-sheaths. Clothing hairs uni- 

 seriate trichomes with muriculate walls. Epidermis of the axis 

 one-layered. Pericycle of isolated bast fibres. Vessels numerous. 

 Interfascicular wood prosenchyma not extensive. 



Phyllanthus niruri L.— Fig. 295. Epidermal cells of the 

 leaf with outer walls a little papillose. Internal secretory cells with 

 tanniniferous contents in the spongy tissue. Numerous solitary 

 crystals in the palisade tissue, Veins without bundle-sheaths. 

 Clothing hairs thick- walled and unicellular or septate. Epidermis 

 of the axis two-layered. Collenchyma in the ribs of the axis. 

 Pericycle forming a loose ring of groups of bast fibres. Vessels few. 

 Interfascicular wood prosenchyma extensive. 



Structure of the leaf. — Epidermal cells have outer walls thickened 

 and papillose, papillae being large and conspicuous in E. granulata 

 (fig. 294). Inner walls are also a little thickened. Lateral walls are 

 thin and straight. Stomata are more numerous on the lower surface 

 and are accompanied by ordinary epidermal cells. Guard-cells are in 

 the plane of surrounding cells and the front cavity is placed in a 

 depression formed by papillae. 



The mesophyll is bifacial. Internal secretory organs are repre- 

 sented by numerous large polygonal cells with tanniniferous contents 

 in the spongy tissue in the leaf of P. Niruri. In the axis of E. gran- 

 ulata there are numerous thick-walled elliptical cells with tanninifer- 

 ous contents, interposed between the groups of bast fibres. Internal 

 secretory cells are absent in the leaf and axis of E. granulata and 

 P. Niruri respectively. Oxlate of lime is found in the form of 

 numerous solitary crystals in the palisade tissues of the leaf in P. 

 Niruri. 



Veins are embedded and are enclosed in distinct green bundle- 

 sheaths in E. granulata. Bundle-sheaths are not found in P. Niruri. 



Structure of the axis — The epidermis in P. Niruri is two- 

 layered ; cells of the outer layer have outer walls greatly thickened 

 and granulated. Epidermis in E. granulata is single layered ; epider- 



