162 THE JOURNAL OP INDIAN BOTANY. 



parenchymatous and hold tanniniferous contents in both the mem- 

 bers. 



Wood forms of a composite hollow cylinder in G. polygonoides, 

 while in P. plebejum it consists of xylem bundles connected by strands 

 of interfascicular wood prosenchyma. Vessels in G. polygonoides are 

 small and few; they are uniformly distributed in extensive interfasci- 

 cular wood prosenchyma formed of small cells with thick walls and 

 with small lumina. Medullary rays are present only in C. polygonoi- 

 des and are 1-2 seriate. Vessels in the xylem bundles of P. plebejum 

 are many and large and the connecting strands of interfascicular 

 wood prosenchyma are formed of cells with thin walls and with large 

 lumina. Wood parenchyma is little developed. 



Pith consists of thin-walled and thick-walled cells in P. plebejum 

 and G. polygonoides respectively. 



Oxalate of lime is found in the form of clustered crystals in the 

 assimilatory tissue and in cortical parenchyma near the pericycle. 

 Secretory cells with tanniniferous contents occur in the epidermis, 

 cortical parenchyma and pith in species of both the genera, Tannin 

 is also found in the medullary ray-cells of G. polygonoides. 



The mechanical tissue consists of sub-epidermal strands and of 

 pericyclic stone-cell groups. Sub-epidermal strands are collenchy- 

 matous in P. plebejum, while those in G. polygonoides are formed of 

 stone-cells. Sub-epidermal strands and the pericyclic stone cell groups 

 together form a system of I-girders, the webs being formed by the 

 assimilatory tissue. The occurrence of the mechanical tissue in the 

 form of I-girders in the periphery of the axis forms a suitable 

 strengthening tissue in the axis which is exposed to the strong winds 

 of the desert. 



AR1STOLOCHIACEAE. 



Aristolochia bracteata Eetz. — Epidermis of tabular cells. 

 Stomata found on both the surfaces and accompanied by ordinary cells. 

 Mesophyll bifacial. Clothing hairs uniseriate and bracket-shaped. 

 Veins embedded and with bundle-sheaths. 



Structure of the leaf. — The epidermis consists of tabular cells 

 with outer walls thickened and convexly arched outwards. Late- 

 ral 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 outer thickened epidermal walls. 



Hair convering consists of a few clothing hairs which are 

 uniseriate and bracket-shaped. They are composed of a unicellular 

 dome-shaped pedestal seated on epidermal cells, of a neck and of a 



