100 THE JOURNAL OF INDIAN BOTANY. 



lime absent. Veins without bundle-sheaths. Clothing hairs uniseri- 

 ate trichomes. Glandular hairs spherical. Epidermal cells of the 

 axis with outer and inner walls thickened. T. S. of the axis qua- 

 drangular. Collenchyma in the angles. Pericycle of stone-cells groups. 

 Assimilatory tissue in the axis of palisade cells. Endodermis differ- 

 entiated and with radial walls suberised. Wood composite. Interfasci- 

 cular wood prosenchyma extensive and composed of cells with thick 

 walls and with small lumen. Medullary rays uniseriate. Pith of thin- 

 walled cells. 



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

 with the outer walls very greatly thickened. The cells on the upper 

 side are larger than those on the lower. The lateral walls are thin 

 and straight. 



The stomata occur on both the surfaces and are accompanied by 

 subsidiary cells. The guard-cells are elevated and the front cavity is 

 placed in a depression formed by outer thickened epidermal walls. 

 The mesophyll is composed of palisade tissue on the upper side and of 

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

 do not occur in the leaf or axis. The veins are not enclosed in bun- 

 dle-sheaths. The leaves are many-ribbed. The veins of the ribs are 

 vertically transcurrent above and below by colourless parenchyma. 



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

 glandular hairs. Clothing hairs are in the form of uniseriate tricho- 

 mes with verrucose walls (fig. 266). They are more numerous on the 

 lower surface. The trichomes on the axis are much longer ; but are 

 otherwise like those on the leaf (fig. 267). External glands occur in 

 two forms on the leaf and axis. They either consist of a short uni- 

 seriate stalk and of a spherical unicellular head, or are formed of a 

 stalk-cell an3 of a bladder-like head the cuticle of which is raised like 

 a bladder, owing to the accumulation of secretion. 



Structure of the Axis. — The T. S of the axis is quadrangular in 

 outline with shallow grooves between the angles. The epidermis 

 consists of small tabular cells with the outer and inner walls 

 thickened. The outer walls are convexly arched outwards. The 

 internal walls are thin and straight. The cuticle is thick. The 

 cortex (fig. 267) is characterised by subepidermal strands of collen- 

 chyma situated in the angles. The assimilatory tissue consists of 

 strands of palisade cells between the collenchyma at the angles. The 

 endodermis is distinct and consists of thin-walled cells with radial 

 walls suberised. 



The pericycle is composed of groups of stone-cells at the angles 

 (fig. 267). The wood is composed of large xylem bundles at the 

 angles and of small ones between fchem. The interfascicular wood 



