64 THE JOURNAL OF INDIAN BOTANY. 



The scantiness of the veins is characteristic of leaves of herba- 

 ceous members, while their abundance and anastomosis distinguish 

 the leaves of woody members. Though the veins are numerous in the 

 latter, transpiration is arrested by the thickened and cuticularised 

 outer epidermal walls, by the poorly developed ventilating system and 

 by the abundance of tannin in cells of the mesophyll. 



The clothing hairs on the leaf and axis in all members except 

 H. supinum are characterised by calcification of their walls which are 

 consequently verrucose and rough. Some of the epidermal cells In 

 these members undergo a division by vertical walls as in (fig. 210) and 

 elongate as shown in (figs. 207, 208, 209). The walls of the terminal 

 portion are secondarily impregnated with calcium carbonate. The 

 hairs thus formed are unicellular, conical and have a broad thin-walled 

 base. They are found in the leaf and axis of all members except 

 H. supinum. Besides these, there are found other forms of clothing 

 hairs in the different members. In E. aspera (fig. 202), T. indicum 

 (fig. 218) and A. hispidissima (figs. 221, 222, 223) are found unicellular 

 hairs which have a thin-walled bulbous base and a tapering terminal 

 portion with walls, verrucose or smooth as in H. supinum. Hairs in 

 H. undulatum consist of a thin- walled basal cell and of a long appres- 

 sed terminal cell with verrucose walls. Cystolith-like structures 

 occur in the basal portions of the hairs of S. pauciflorum, A. hispidis- 

 sima, H. rariflorum and H. undulatum, T. indicum. 



It should be observed in all these forms of hairs that the basal 

 portion is bulbous and thin-walled and it may be a means of absorbing 

 water trickling down the terminal portion. Hairs, when not 

 numerous, are more or less appressed as in E. aspera and H. undu- 

 latum and they form a suitable light screen. 



Glandular hairs are not common. They are found in a very small 

 number in H. supinum, and they consist of a stalk-cell and of a 

 spherical unicellular head. 



Structure of the Axis : — The epidermal cells have outer walls 

 thickened and cuticularised in all members except the herbaceous 

 ones. The lateral walls are usually thin and undulated. Some of the 

 epidermal cells in T. indicum and S. pauciflorum are large and verti- 

 cally elongated (figs. 217, 220); and give rise to a somewhat ribbed 

 appearance to the axis. These cells may have the function of giving 

 rigidity to the epidermal tissue. The primary cortex is generally 

 characterised by an assimilatory tissue which consists either of pali- 

 sade cells as in H. undulatum (fig. 214), or of arm-palisade tissue as 

 in S. pauciflorum (fig. 220) and A. hispidissima, or of chlorenchyma 

 as in E. Aspera, H. supinum, H. panic ulatum (fig. 216) and T. indicum. 

 There is a two-layered tissue of large thin-walled, colourless tabular 



