98 THE JOURNAL OP INDIAN BOTANY. 



TAMARISCINEAE. 



Tamarix dioica Boxb — PI. VI, fig. 45. Epidermal cells with 

 inner walls a little more thickened than outer walls. Pits not deep. 

 Cortical parenchyma of small cells. Sclerenchymatous pericycle more 

 or less forming a loose ring of stone-cells with interposing cells 

 thickened and radially striated. Wood forming a composite hollow 

 cylinder. Soft hast forming groups. Medullary rays 2-6 seriate. Pith 

 composed of thick-walled cells. 



Tamarix orientalis Forsk.— Fig. 46. Epidermal cells with 

 outer and inner walls thin. Pits quite deep. Cortical parenchyma 

 formed of large thin-walled cells. Sclerenchymatous pericycle more 

 or less isobilateral. Wood forming a composite central cylinder 

 without a central pith tissue. Soft bast forming a continuous ring. 

 Medullary rays uniseriate and few. 



Structure of the Axis : — The epidermis consists of thin- walled 

 horizontally tabular cells. The front cavity is depressed and closed 

 above and below by thin walls, fig. 45. The guard-cells are in the 

 plane of or in a plane lower than that of the surrounding cells. 



Clothing hairs are not found on the axis of either of the species. 

 External glands, figs. 45, 46, are placed in pits ; they form spherical 

 structures divided by horizontal and vertical three-wall into four thin- 

 walled cells, and are. accompanied on their inner side by two depressed 

 epidermal cells which form the subsidiary cells of the glands. The 

 glands do not project above the surface ; they secrete hygroscopic 

 salts which fill the pits and absorb moisture from the air outside. 



The primary cortex is characterised on its outer side by an assi- 

 milatory tissue of palisade cells and on its inner side by cortical 

 colourless parenchyma. There are numerous water-storing tracheids 

 in the cortical parenchyma with pitted or scalariform thickenings, 

 the larger ones being accompanied by a few stone-cells. Cortical 

 parenchyma forms an aqueous tissue and in T. orientalis is composed 

 of large thin-walled cells. 



The pericycle is composed of large groups of stone-cells. The 

 stone-cell groups in T. dioica are closely placed all round the soft bast 

 and the cells interposed between them are characterised by sclerosis 

 and by radical striation of the wall. In T. orientalis stone-cell 

 groups are placed on two opposite sides in the form of arcs and the 

 cells interposed between them are thin-walled and parenchymatous. 

 The sides possessing the stone-cell groups may perhaps represent the 

 plane of the axis most affected by the wind ; and the stone-cell groups 

 may have been developed in that plane to protect the axis against 

 violent shaking by the wind. 



