654 JOURNAL, BOMBAY NATURAL HISTORY SOCIETY, Vol. XVI. 



Fig. 1, Plate B, shows a small portion of the under surface of a 

 leaf of Rhizophora mucronata. The epidermis, which is composed of 

 a single layer of cells, is on the inside distinctly marked off from the 

 neighbouring tissue. The outer walls of the epidermal cells are consider- 

 ably thickened and even the side-walls show some thickening. Though 

 the guard-cells always have their walls thickened in a peculiar way, they 

 attain a still higher development in this direction in Rhizophora mucro- 

 nata. The outermost layer of the external walls being in our case ex- 

 ceedingly well developed, covers as a cuticle the whole surface of the 

 epidermis, leaving open small passages only for transpiration. The 

 respiratory cavities, which communicate directly with the intercellular 

 spaces of the spongy parenchyma, are comparatively small. A complete 

 transverse section would show that the number and area of those 

 intercellular spaces is greatly reduced. 



Fig. 2, Plate B, exhibits a small portion of a transverse section of a 

 leaf of Sonneratia acida, showing the epidermis with stomata. The 

 epidermis is strongly cuticularised, even the side-walls of the epidermal 

 cells exhibit greater cuticularisation than those of Rhizophora mucronata. 

 The stomata, which are somewhat raised in the foregoing figure, are 

 here on the same level with the epidermal cells and thus under the 

 horizontal band of the cuticula. 



Sometimes one may observe near the sea-shore that individuals of 

 the same species grow in the salt water as well as in the common soil. 

 The comparative anatomy of their leaves shows the special adaptations 

 to the respective substratum far clearer than does the comparison 

 between plants belonging to different species. Fig. 3, Plate B, gives 

 the diagrammatic view of the transverse section of a leaf of Sonneratia 

 acida growing in salt mud, and Fig. 4 that of the same growing in 

 common soil. In Fig. 4 the palisade-tissue is much reduced, whereas in 

 Fig. 3 it is well developed near the ventral as well as near the dorsal 

 surface. The same reduction -is observed in the spongy parenchyma, 

 and, what is most important, the mangrove growing in the salt mud has 

 developed more and greater vascular bundles. As the ramifications of the 

 vascular bundles are prolonged, the bundles themselves become smaller 

 and smaller and, finally, are of very simple structure. When the vessels 

 disappear, there remain only spirally and reticulately thickened tracheids, 

 which prove to be excellent channels for the conduction of water. (Fig. 5, 

 Plate B, shows the termination of vascular bundles with tracheids.) 



