94 THE JOUENAL OF INDIAN BOTANY. 



thickened and convexly arched outwards. There are large unicellular 

 conical hair-like structures, with walls covered with cuticular knobs, 

 intercalated amongst ordinary epidermal cells (fig. 246). The lateral 

 walls are thin and undulated. The inner walls are thin. The cuticle 

 is striated. The stomata are equally numerous on both the surfaces 

 and are surrounded by ordinary epidermal cells. The guard-cells are 

 elevated and the front cavity is on a level with the surface. 



The mesophyll is bifacial. Internal secretory organs and oxalate 

 of lime are not found. The veins are embedded and are not enclosed 

 in bundle-sheaths. The hairy covering on the axis consists of thin- 

 walled uniseriate trichomes. Trichomes in S. sphaerocarpa are cover- 

 ed with cuticular knobs. Large conical epidermal cells with walls 

 covered with cuticular knobs (figs. 246, 247) may be of the nature of 

 unicellular hairs in S. sphaerocarpa- The trichomes in A. linearis 

 are smooth-walled and straight. Glandular hairs are not found. 



Structure of the Axis. — Epidermis consists of tabular cells with 

 outer walls greatly thickened and convexly arched outwards. Cuticle 

 is striated. There are large concical unicellular hair-like structures 

 with walls covered with cuticular knobs intercalated amongst ordinary 

 epidermal cells in S. sphaerocarpa (fig. 247). Lateral walls are thin 

 and straight. The stomata are like those on the leaf. The cortical 

 parenchyma is composed of horizontally elongated cells. The cells of 

 the outermost layer of the cortex show collenchymatous differenti- 

 ation at angles in contact with the epidermal cells. 



The pericycle consists of a few isolated bast fibres and of a loose 

 ring of groups of bast fibres in S. sphaerocarpa (fig. 247) and A. linea- 

 ris (fig. 245J respectively. The wood forms a composite hollow cylin- 

 der. The vessels in S. sphaerocarpa (fig. 247) are arranged in com- 

 plete rows ; interfascicular wood prosenchyma is little developed and 

 is composed of cells with thin walls and with large lumen. The ves- 

 sels in A. linearis are small and are arranged in long incomplete rows ; 

 the interfascicular wood prosenchyma is extensive and is composed of 

 cells with thick walls and with small lumen. The medullary rays 

 are uniseriate and numerous in A. linearis; they are absent in 

 S. sphaerocarpa. The pith is composed of thin-walled cells. 



ACANTHACEAE. 



Blepharis sindica T. Anders.— Figs. 248, 249, 250. Outer 

 walls of epidermal cells greatly thickened. Guard-cells elevated. 

 Front cavity on a level with the surface. Mesophyll formed of pali- 

 sade tissue on the upper side and of subepidermal aqueous tissue and 

 palisade tissue on the lower. Veins provided with bundle-sheaths. 



