60 Journal of the Asiatic Society of Bengal [February, 1914. 



clearest manner in Zoysia pungens, Wil:d. I shall first very 

 briefly indicate the adaptations in the general configuration ol 

 the plant and then pass on to examine in detail the structural 



peculiarities in the leaf. 



To begin with, the prostrate attitude of the plant (Plate 



V, Fig. A) appears to be solely due to the action of high 

 v/inds prevalent on the sea-shore. The presence of numerous 

 long adventitious roots with an interlacing system of rootlets 

 helps to anchor the plant firmly in the loose shifting substratum 

 and thus offers a protection against violent winds. The very 

 short, stiff, leafv stems do not offer much resistance to the 

 blowing wind. The growing tip of the plant (Plate V, Fig B). 

 is so finely pointed that it quite easily pierces the sand. 

 Moreover, as pointed out by Sohimper, these plants have the 

 wonderful faculty of again growing out of the sand after having 

 been covered by it. A tendency to diminish the evaporating 

 surface and to conserve the stock of water is also shown by the 

 rigid, subulate leaf, hard in consistency and with a spiny apex. 

 The du'l light green colour of the leaf is also an adaptation, 

 which this plant possesses in common with other sand plants, 

 to ward off the great intensity of light on the sea-shore. 

 Having briefly outlined the general adaptations 1 now proceed 

 to point out the various structural adaptations found in the 

 tissues composing the leaf of Zoysia pungens, Willd. 



Epidermis. — Under this heading, we have to consider not 

 only the ordinary epidermal cells but also the "motor 

 cells" and the stomata. The epidermal cells appear more or 

 less square in transverse section, while in longitudinal section 

 they appear rectangular. They are, as usual, arranged along 

 the' long axis of the leaf. As regards their form, the outer 

 walls of the upper epidermal cells are conspicuously arched 

 outwards, while those of the lower are much flatter. In the 

 former, the arching of the outer walls has taken place to such 

 an extent, as to make the cells distinctly papillose. The purpose 

 of these papillae will be referred to later. Both the upper and 

 the lower epidermis are much thickened, but the difference 

 between them in the amount of thickening is very marked. The 

 lower epiderm s is much more thickened than the upper. This 

 is explained by the fact that the upper epidermis in these grasses 

 almost always remains protected by the rolling or folding of the 

 leaf, which not intrequently happens in grasses enduring along 

 season of drought. Consequently, the upper epidermis does 

 not stand in need of much thickening, whereas the lower 

 epidermis is constantly exposed and therefore requires to be 

 considerably thickened. This exceptionally strong cuticularisa- 

 tion of the lower epidermis, then, is an adaptation against 

 excessive transpiration and excessive light, as the layers forming 

 the cuticle are tilled with air and act as bad conductors between 

 the external atmosphere and the internal structures. 



