PLANTS OF THE INDIAN DESERT. 95 



Clothing hairs unicellular and conical. Glandular hairs formed of a 

 stalk-cell and of a spherical head divided by horizontal and vertical 

 walls. Crystal sand in the clothing hairs of the leaf and in epidermal 

 cells of the axis. Collenchyma forming a continuous ring. Aqueous 

 tissue occurring below collenchyma. Pericycle in the form of isolated 

 bast fibres. Vessels uniformly distributed in the wood-ring. Inter- 

 fasciculer wood prosenchyma fairly extensive. Wood parenchyma 

 fairly extensive- Medullary rays few and uniseriate. Pith of thin- 

 walled cells. 



Ruellia patula J acq.— Fig. 251. Guard-cells elevated. Front 

 cavity on a level with the surface. Mesophyll of palisade tissue on 

 the upper side and of arm-palisade tissue on the lower. Veins not 

 provided with bundle-sheaths. Clothing hairs uniseriate and more or 

 less jointed. Glandular hairs with an uniseriate stalk and with a disc- 

 shaped head divided by horizontal and vertical walls. Assimilatory 

 tissue in the axis parenchymatous. Structures resembling internal 

 glands found in cortex. Pericycle of a few isolated bast fibres. Wood 

 composed of large bundles at the angles and connected by strands of 

 interfascicular wood prosenchyma. Wood parenchyma in groups on 

 the inner side of xylem bundles. Medullary rays uniseriate. Pith of 

 thick-walled cells. 



Barleria hochstetteri Nees — Figs. 252, 253, 254, 255, 256, 257. 

 Guard-cells in the plane of surrounding cells. Mesophyll isobilateral. 

 Veins without bundle-sheaths. Structures resembling internal glands 

 present. Clothing hairs on the leaf short and unicellular, and those 

 on the axis in the form of armed trichomes. Glandular hairs with an 

 uniseriate stalk and with a disc-shaped head divided by a vertical wall. 

 Collenchyma strengthening the ribs. Assimilatory tissue in the axis 

 parenchymatous. Sclerenchymatous pericycle not developed. Vessels 

 uniformly distributed in the wood-ring. Wood narrowed at two 

 opposite points. Medullary rays uniseriate. Interfascicular wood 

 prosenchyma little developed. Pith of thin-walled cells and retained. 

 Pith cells with acicular or rod-like crystals. A thick-walled vessel 

 present in pith. 



Justicia simplex Don.— Fig. 258, 259. Guard-cells elevated or 

 in the plane of surrounding cells. Mesophyll isobilateral. Structures 

 resembling internal glands found in the mesophyll. Veins without 

 sheaths. Clothing hairs short and uniseriate. Glandular hairs with a 

 stalk-cell and with a spherical head divided by horizontal and vertical 

 walls. Assimilatory tissue in the axis formed of palisade cells. Collen- 

 chyma developed at the angles of the quadrangular axis. Scleren- 

 chymatous pericycle not developed. Wood composed of xylem bun- 

 dles at the angles connected by strands of interfascicular wood pro- 



