6 THE JOUENAL OF INDIAN BOTANY. 



The wood is composed of xylem bundles or forms a composite 

 hollow cylinder, as will be seen from the tabular form. Vessels have 

 simple perforations. The interfascicular wood prosenchyma is well 

 developed only in V. cinerascens (fig. 165), P. senegalensis and P. raj- 

 patanae (fig. 173) ; medullary rays are found only in these members. 

 Other members are more or less herbaceous and the structure of 

 wood does not follow any definite lines of development, as it is found 

 to vary in the same species. 



The wood parenchyma is little developed and occurs on the inner 

 side of fehe xylem bundles. The pith consists of thin-walled cells in 

 all members except V. cinerascens and P. rajputanae where it is formed 

 of cells with thick and lignified walls. Some of the pith cells of 

 P. rafpidanae contain black granular contents (fig. 173 G). 



Anamolous structures are represented by small medullary xylem 

 bundles close to the inner side of the wood cylinder of P. rajputanac 

 (fig. 173 C). 



SALVADORACEAE. 



Salvadora persica L.— Figs. 191, 192, 193. Epidermis of the 

 leaf locally two-layered. Larger veins with arcs of stone-cells on the 

 lower side. Vascular ring more or less dumb-bell shaped. Vessels in 

 the narrowed portion very small. Soft bast forming a continuous ring 

 and following the outline of the wood cylinder. 



Salvadora oleoides Dene.— Figs. 194, 195, 196. Epidermis 

 of the leaf uniformly two-layered. Vains with sclerenchyma on their 

 upper and lower side. Short unicellular hairs found on branches. 

 Wood forming a hollow cylinder of uniform breadth. Medullary rays 

 continuous with cortical parenchyma. Soft bast forming groups. 



Structure of the Leaf. — The epidermis in S. persica (fig. 191) is 

 locally two-layered. The epidermal cells are tabular with outer walls 

 thickened. The inner and lateral walls are also a little thickened and 

 the former are convexly arched inwards. The epidermis in S. oleoides 

 (fig, 194) is uniformly two-layered on both sides. The outer layer is 

 formed of small tabular cells with the outer and lateral walls thicken- 

 ed ; the inner layer consists of large thin- walled tabular cells with the 

 inner walls convexly arched inwards, so as to come into close contact 

 with the assimilatory tissue. There are a few large thick- walled ovoid 

 epidermal cells found below the epidermis on both sides in either 

 species; these cells probably have a water-storing function. 



The sfcomata are associated with subsidiary cells and occur abund- 

 antly on both the surfaoes. The guard-cells are situated in the plane 

 of surrounding cells. The front cavity is usually situated in the de- 



