160 THE JOUKNAL OF INDIAN BOTANY. 



the clustered crystals in the "aqueous tissue, there is a continuous 

 layer of rounded thin-walled cells, most of which contain clustered 

 crystals ; it is situated beneath the sub-epidermal aqueous tissue 

 in H. salicornicum. It may be termed a crystal layer. 



General Review. — Epidermal cells have outer walls thin and 

 more or less papillose. Stomata are depressed and guard-cells are 

 situated in the plane of surrounding cells. The assimilatory tissue 

 in the leaf and axis consists of palisade cells. The leaf and axis are 

 characterised by the extensive development of an aqueous tissue, 

 either peripheral, or central or both. The vascular system in the 

 leaf consists of peripheral and central veins ; and it is brought into 

 contact with the assimilatory tissue by means of sheath-cells. Hairy 

 covering, when present, consists of uniseriate trichomes densely 

 covered with solid papillae. Oxalate of lime occurs in the form of 

 clustered crystals in the leaf and axis. 



Sclerenchymatous pericycle is found in all the members. The 

 vascular system in the axis consists of bundles traversing the aqueous 

 tissue as found in species of Haloxylon and of a central cylinder as 

 found in all the members. Bundles in the central cylinder are 

 embedded in interfascicular wood prosenchyma in a concentric fashion. 

 Vessels are small and have simple perforations. Medullary rays are 

 not found in any of the members. 



POLYGONACEAE. 



Calligonum polygonoides L— Figs. 291, 292, Woody. 

 Mesophyll isobilateral with a middle layer of cells with tanniniferous 

 contents. Palisade-like cells with tanniniferous contents in the palisade 

 tissue. Clothing hairs in the form of uniseriate trichomes. External 

 glands club-shaped. Epidermal cells of the axis with outer walls very 

 greatly thickened. Subepidermal groups of sclerenchyma present. 

 Clustered crystals in the primary cortex. Pericycle of small groups 

 of stone-cells. Wood composite. Interfascicular wood prosenchyma 

 extensive. Meduallary rays 1-2 seriate and numerous. Pith of thick- 

 walled cells. 



Polygonum plebejum Br.— Wig. 293. Woody. Large water- 

 storing cells intercalated amongst epidermal cells. Mesophyll of pali- 

 sade tissue on the upper side and of arm-palisade tissue on the lower. 

 Clustered crystal in the mesophyll. Bundle-sheath cells with tannini- 

 ferous contents. 



Epidermal cells of the axis with outer walls granulated. Collen- 

 chyma groups subspidermal. Wood composed of xylem bundles. Pith 

 of thin-walled cells. 



