2L8 THE JOUKNAL OF INDIAN BOTANY. 



pact structure. Lateral walls are thin and straight. The upper 

 epidermis forms the aqueous articulation tissue and is many-layered in 

 species of Cy per its. The articulation tissue in the mid-rib of G. rotundas 

 (fig. 303) and S. mar Minus consists of elongated cells narrowed above 

 so as to form a specialised articulation tissue to regulate the upward 

 curving movements of the leaf-halves by the difference in the turgi- 

 dity of these cells. As these cells are greatly narrowed in their upper 

 portion, the leaf-halves can come quite close together and thus 

 protect the articulation tissue from suffering much loss of water in 

 times of very dry weather. Such a tissue in the mid-rib is not 

 necessary in other species of Cyperus, as there is abundant aqueous 

 tissue and as the leaf-halves are very short. In F. tenera the articu- 

 lation is 2-3-layered in the mid-rib. 



Margins are rounded in C. rotundas or are bluntly pointed as in 

 other species of Cyperus and in S. maritimus or peculiarly angular 

 in F. tenera (fig. 308). 



Stomata in species of Cyperus and in F. tenera occur only on the 

 lower surface of the leaf ; in S. maritimus they are more numerous 

 on the lower surface. The occurrence of stomata only on the lower 

 surface is due to the presence of the assimilatory tissue below the 

 lower epidermis ; their presence on the upper surface, where the 

 articulation tissue is developed, will accelarate transpiration and 

 will thus perform a function opposite to that of the articulation 

 tissue. The occurrence of stomata on both the surfaces in S. mariti- 

 mus is partly due to the absence of aqueous tissue near the surface 

 and partly to the presence of photosynthetic tissue along both the 

 surfaces. The guard-cells are elevated and are accompanied by 

 subsidiary cells in all the members. The front cavity is placed on a 

 level with the surface in C. rotundas, while in other species of 

 Cyperus and in S. maritimus it is placed in a depression formed by 

 outer thickened epidermal walls ; in F. tenera it is elevated above the 

 surface. 



The stomata on the leaf as well as those on the axis of all mem- 

 bers have on obconical sub-stomatal cavity which is lined by elongat- 

 ed cells forming an obconical tissue. The obconical cavities are quite 

 conspicuous in C. conglomerates (figs. 299, 303, 302) and also occur 

 below the epidermis even where stomate do not occur. The obconi- 

 cal shape of sub-stomatal cavities and also that of the sub-stomatal 

 tissue forms a characteristic feature of members of Cyperaceae. Stomata 

 occur on the outer surface of the leaf-sheath of S. maritimus. Stomata 

 on the leaf-sheath as well as those on the axis like those on the leaf. 



The photosynthetic tissue in species of Cyperus and in F. tenera 

 is composed of complete girders of tubular palisade cells round all the 



