458 A NATURALIST IN THE PACIFIC chap. 



presented itself to him, but only in connection with the means 

 employed in some of the genera, as with Bruguiera, for conveying 

 nourishment to the growing embryo. He remarks that he was 

 involuntarily reminded by these structures of the chorion-tufts and 

 lobes in the placenta of mammals, and that such structures in the 

 mammal are functionally nothing more than true haustoria as found 

 in the viviparous mangroves. 



When studying the germination of the American and Asiatic 

 Rhizophoras in Fiji, I observed that the neck of the cotyledonary 

 body did not begin to form, nor the inclosed plumular bud to show 

 signs of differentiation, until the hypocotyl had protruded about 4^ 

 inches with R. mangle, and between 6 and 7 inches with R. mucro- 

 nata. The neck of the cotyledonary body then proceeds to grow 

 in length, pushing before it the plumular end of the embryo-seed- 

 ling, which it surrounds as a sheath. This operation continues 

 until the hypocotyl has acquired a length of about seven inches 

 with R. mangle, and about nine inches with R. mucronata, when 

 the neck begins to protrude outside the fruit. The cotyledonary 

 neck proceeds with its growth, and by the time the seedling is 

 ready to fall from the tree it protrudes about an inch from the fruit- 

 shell, having carried the growing plumular bud with it. The 

 plumular end of the seedling has been now more or less expelled 

 from the fruit-cavity, and the connection between the suspended 

 seedling and the fruit now alone depends on a slight bond between 

 the base of the plumule and the inner margin of the cotyledonary 

 neck, as indicated by a cross in the figures given in the plate. The 

 union is soon broken and the seedling falls. 



Whether there is anything more than an analogy between the 

 expulsion of a Rhizophora seedling and the birth of a mammal 

 seems most unlikely ; but the process is at all events a very re- 

 markable one. 



The means of dispersal of the genus Rhizophora 



My experiments and observations were for the most part made 

 on the Asiatic and American species in Fiji ; but I enjoyed the 

 opportunity of confirming some important points on the coast of 

 Ecuador. We can only look to the currents for the explanation of 

 the capacity of the genus to cross tracts of ocean ; but, given this 

 capacity, there is much that is difficult to understand in the distri- 

 bution of the genus and of a species like Rhizophora mangle ; and 

 it is probable that we shall have to look behind the means of 



