PLANTS OF THE INDIAN DESEET. 99 



are thin and straight. The stomata occur on both the surfaces and 

 are accompanied by subsidiary cells in B marrubi/olia and by 4 or 5 

 ordinary epidermal cells in C. Phlomidis. The guard-cells are a 

 little elevated and the front cavity is placed in depressions formed by 

 thickened outer epidermal cells. 



The mesophyll is composed of palisade tissue on the upper 

 side and of arm-palisade tissue on the lower. Internal secretory 

 organs and oxalate of lime are found neither in the leaf nor in the 

 axis. The veins are embedded and are not provided with bundle- 

 sheaths. 



The hairy covering on the leaf and axis consists of clothing and 

 glandular hairs. Clothing hairs occur in the form of unicellular or 

 bluntly pointed uniseriate trichomes with muriculate walls. The 

 clothing hairs are more numerous on the lower surface. The glandu- 

 lar hairs are placed in epidermal depressions. They are composed in 

 C. Phlomidis of a stalk-cell and of a broadly disc-shaped head divided 

 by many vertical walls (fig. 264). In B. marrubi/oli (fig. 262), they 

 consist of a short uniseriate stalk and of a disc-shaped head divided 

 by an oblique wall. 



Structure of the Axis. — The epidermal cells are tabular, with 

 outer walls thickened and muriculate in B. marrubi/olia, and thin and 

 convexly arched outwards in C. Phlomidis. The lateral walls are thin 

 and straight. The primary cortex is composed on its outer side of 

 collenchyma and on its inner side of cortical parenchyma. Cork is 

 developed below the collenchyma in C. Phlomidis. Cortical paren- 

 chyma is of uniform breadth in G. Phlomidis and is more extensive in 

 the plane exposed to the wind in B. marrubi/olia. 



The pericycle consists of a more or less composite ring of stone- 

 cells in G. Phlomidis and of groups of stone-cells in B. marrubi/olia. 

 The stone-cell tissue is more extensive in the plane exposed to the 

 wind in B. marrubi/olia. The wood forms a composite hollow cylin- 

 der. The vessels are large and are uniformly distributed in incom- 

 plete rows in the extensive interfascicular wood prosenchyma. Me- 

 dullary rays are 1-2 seriate and are numerous. 



The pith consists of thin-walled cells. 



LABIATAE. 



Salvia aegyptiaca L— Figs. 265, 266, 267. Upper epidermal 

 cells larger. Epidermal cells tabular with outer walls very greatly 

 thickened. Stomata on both the surfaces and accompanied by subsi- 

 diary cells. Mesophyll formed of palisade tissue on the upper and of 

 arm-palisade tissue on the lower. Internal glands and oxalate of 



