646 JOURNAL, BOMBAY NATURAL HISTORY SOCIETY, Vol XVI. 



stem find its branches are those stilt-roots which reach a height of 

 2 to 3 yards, and which, on account of their great elasticity, are the 

 best possible protective system against the continuous dashing of the 

 waves. The tree maybe moved forwards and backwards by the force of 

 wind and water, but, ultimately, it will always assume its former posi- 

 tion. In this way the aerial roots are like as many strong anchors which 

 would not allow the tree to be carried away even by the wildest play of 

 the waters. We may very often observe that the growing point of such 

 a root loses its vitality, whereas behind the apex a forked root makes 

 its appearance. It is evident that such a change of growth can have 

 a beneficent influence only under the conditions of existence in a 

 soft and muddy substratum. Another means of furnishing the tree 

 with considerable resisting power is the circumstance that not 

 seldom a row of secondary roots breaks through the under surface 

 of the primary aerial root, descends immediately in a vertical 

 direction into the mud, and, by a luxurious branching into roots 

 and rootlets, helps to strengthen the primary root. The most peculiar 

 feature of Rhizophora mucronaia and also, as regards the essentials, 

 of the other Rhizophoraceee is the mode of reproduction. If, 

 after the flowering season (August-December), we approach a 

 manorove vegetation from the sea-side, we are surprised to see, 

 from a distance long, green pods hanging from the branches of 

 the true mangrove ; but on closer examination we find that 

 what we naturally took for a fruit is nothing else than the 

 radicle of a comparatively small fruit, which does not exceed 1^ 

 in. in length. Here we have an excellent case of vivipary in the 

 vegetable kingdom, the extra-seminal development of the embryo 

 beginning already while the fruit still adheres to the tree. The 

 hypocotyl, passing posteriorly into the primary root or radicle, 

 perforates without having a resting period, the morphological apex of 

 the pericarp and protrudes into the air reaching sometimes a length of 

 2 ft. Brandis speaks of 2 \ ft., and Haberlandt * observed radicles of 

 one yard in the mouth of the Sairomggong River on the Island of Singa- 

 pore. At the upper end the radicle is about \ in. in diameter, it grows 

 thicker towards the lower end, with a diameter of 1 in. and more, and 

 tapers into a conical point at the apex (Fig. 1, Plate A). There 

 cannot be any doubt as to the importance of this special shape, because, 



* Haberlandt : Eine Botanische Tropenreise,, p. 186. 



