222 THE JOURNAL OF INDIAN BOTANY. 



in a single ring of stone-cells. In S. maritimus veins as well as the 

 vascular bundles in the axis are enclosed in an outer ring of large 

 colourless polygonal cells and in an inner ring of stereome. 



The mesophyll in 0. rotundus and in S. maritimus is character- 

 ised by a system of lysigenously formed cavities resulting from a de- 

 ficient supply of water. Internal secretory cells with tanniniferous 

 contents are numerous near the veins in the leaf and in the neighbour- 

 hood of vascular bundles in the axis. The mechanical tissue in the 

 leaf as well as in the axis is mostly composed of isolated sub-epidermal 

 girders except in 'the leaves of S. maritimus in which I-girders are 

 found. Vascular bundles in the axis are numerous and peripheral, 

 larger bundles alternating with the smaller. 



The ground tissue is composed of thin-walled parenchymatous 

 cells with a differentiated central tissue of much larger cells in G. ro- 

 tundus. The ground tissue in S. quinquefarius is characterised by 

 large air spaces. S. quinquefarius occurs always on wet ground and 

 well developed aerenchyma is consequently quite necessary. 



The axes of S. maritamus are enclosed in close fitting leaf-sheaths 

 which protect the axes against insolation and also give, to some 

 extent, rigidity to the axes against the violence of the desert winds. 

 Leaf-blades which are as long as the axis are held in position by 

 means of leaf-sheaths and cannot therefore be easily separated from 

 the axis by the strong desert winds. The long leaf-blades, but for 

 the leaf-sheaths, would have been torn off from their bases by the 

 desert winds. 



Hairs either clothing or glandular are not found on the leaf and 

 axis. 



GRAMINEAE 



Digitaria sanguinalis Scop. var. ciliaris Pram.— Grooved 

 on the lower surface. Hairs spiny on the leaf and absent on the axis. 

 Stomata more numerous on the lower surface. Articulation tissue not 

 extensive and found on the upper side above the grooves. Palisade 

 cells forming complet9 girders. Veins embedded and enclosed in 

 complete sheaths. Mechanical tissue in the leaf in the form of I- 

 girders. Webs formed by unmixed vascular bundles. Mechanical 

 tissue in the axis forming isolated sub-epidermal girders and an intern- 

 al stereome tube. Assimilatory tissue absent in the axis. Smaller 

 bundles embedded in the stereome tube. Large bundles few in the 

 medullary tissue. Medullary tissue of thin-walled cells. 



Panicum turgidum Forsh, — Eigs..319, 320, 321. Equally 

 deeply grooved on both sides. Margins blunt and with large stereo- 

 me bundles. Hairs spiny and absent on the axis. Stomata more 



