158 THE JOUENAL OF INDIAN BOTANY. 



and arched surfaces of the leaf. In sections of the basal portion, 

 the palisade tissue disappears all along the flat surface. Gaps in the 

 palisade tissue are filled in by palisade-like aqueous cells along the 

 flat surface and by polygonal aqueous cells at the angles and along 

 the middle portion of the arched surface. Some of the polygonal 

 aqueous cells at the angles contain large clustered crystals. 



The aqueous tissue consists partly of a I continuous layer of 

 subepidermal aqueous cells many of which contain clustered crystals, 

 and chiefly of a centrally placed mass of large aqueous cells which 

 enclose the central veins as well as the smaller ones lying at the 'peri- 

 phery of the aqueous tissue. The centrally placed aqueous tissue is 

 bounded by a layer of cubical or tabular cells in those parts where 

 the palisade tissue is present in S. foetida and H. recurvum respect- 

 ively. Cells of this layer contain chlorophyll and resemble cells of 

 bundle-sheaths. This layer may assist the assimilatory tissue in car- 

 bon assimilation as well as serve to bring into contact the assimilatory 

 and vascular tissue. Some of the peripheral cells of the central 

 aqueous tissue contain clustered crystals in the neighbourhood of the 

 veins. 



Oxalate of lime is found in the form of clustered crystals which 

 are found in subepidermal aqueous cells as well as in aqueous cells 

 of the central tissue in the neighbourhood of peripheral veins. Inter- 

 nal glands are not found in the leaf and axis of any members. 



The system of veins consists of centrally placed veins, of veins 

 traversing the central aqueous tissue and of peripheral veins situated 

 beneath the sheath-layer which forms a bundle-sheath common to 

 all the veins and which brings into contact the assimilatory and 

 vascular tissues. The central vein in S. foetida is embedded in a 

 cylinder of stone-cells, while that in H. recurvum is surrounded by a 

 tissue of small thin-walled parenchymatous cells. 



Hairy covering on the leaf and axis of S. foetida consists of 

 uniseriate trichomes seated on larger epidermal cells. Hairs are 

 composed of a, basal portion of a few short cells and of an irregularly 

 curved and pointed terminal portion which consists of longer cells 

 with walls covered with solid papillae (fig. 287). Hairs are not found 

 in both the species of Haloxylon. External glands do not occur in 

 any of the members. 



Structure of the Axis. — Epidermal cells in H. recurvum have 

 outer walls thickened and papillose ; those in H. salicornicum are 

 tabular and thin-walled and those in S. foetida are small polygonal 

 cells with outer walls thickened and granulated. Stomata have the 

 same characters as those on the leaf. Primary cortex is characterised 

 by a sub-epidermal continuous layer of collenchyma in S. foetida, by 



