102 THE JOURNAL OF INDIAN BOTANY. 



storage function intercalated amongst the ordinary epidermal cells in 

 Hibiscus micranthus (fig. 57A). They are present on both the sides 

 and have their inner walls convexly arched inwards so as to come 

 into close contact with the assimilatory tissue. 



The stomata are more numerous on the lower surface. The 

 front cavity is placed in a depression formed by the outer thickened 

 and papillose walls. The guard-cells are in the plane of the surround- 

 ing cells as in Abutilon fruticosum and Sida Qrexoioid.es (fig. 53), or 

 they are elevated as in other species. The elevated position of the 

 guard-cells can be accounted for by the occurrence of a dense covering 

 of tufted hairs. The mesophyll is composed of palisade tissue on 

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

 palisade tissue in Sida greioioides is formed of compact cylindrical 

 groups. The mesophyll is characterised by the abundance of internal 

 glands in Sida grewioides, Pavonia arabica and Gossypium herbaceum. 



The internal secretory organs in Gossypium herbaceum are re- 

 presented partly by some of the palisade cells and a layer of polygonal 

 cells above the arm-palisade tissue with tanniniferous contents and 

 partly by mucilaginous secretory cavities with a lining layer of cells, 

 and situated in the middle of the mosophyll and in the arm-palisade 

 tissue. In Pavonia arabica, there are mucilaginous secretory 

 cavities situated in the middle of the mesophyll below the vascular 

 bundles of the veins. In Sida greioioides (fig. 53), there are groups of 

 loosely arranged palisade-like cells, faintly green in colour and placed 

 between groups of palisade cells ; there are also rounded or elliptical 

 structures amongst the arm-palisade cells, also faintly green in colour. 

 These structures in the mesophyll are either schizogenously formed 

 internal secretory cavities or water-storage cells. 



Oxalate lime occurs in the form of clustered crystals near the 

 veins. In the axis clustered crystals occur in the cortex and pith of 

 all species except Pavonia arabica. In Sida grewioides and Pavonia 

 arabica numerous small-clustered crystals occur in the soft bast. 



The veins are embedded except some of the larger veins in 

 Gossypium herbaceum which are vertically transcurrent above and 

 below partly by means of sclerenchyma and mostly by collenchyma. 

 The veins are provided with bundle -sheaths of green thin-walled 



cells. 



The hairy covering consists of densely placed tufted hairs. The 

 rays are unicellular and are sunk directly in the epidermis, so that the 

 hairs seem to be formed by a group of epidermal cells, fig. 55. The 

 rays on the lower portion of the mid-rib are borne on a short 

 multicellular stalk. The hairy covering is denser on the lower 

 surface of the leaf. 



