CHAPTER IX 



THE GERMINATION OF FLOATING SEEDS 



Germination in the floating seed-drift of tropical estuaries. — A strain of vivipary. 

 — Abortive germination of seeds in warm seas. — A barrier to plant dis- 

 persal. — The borderland of vivipary. — Summary. 



The tendency of the floating seed or fruit to germinate in the 

 estuaries of tropical rivers is especially characteristic of the plants 

 of the mangrove-swamps and of their borders. In the Fijian 

 rivers, and particularly in the estuary of the Rewa, where the 

 river-water is usually mixed with that of the sea, there are 

 frequently to be found in a state of germination floating fruits of 

 Barringtonia racemosa, Carapa obovata, Clerodendron inerme, 

 Derris uliginosa, Smythea pacifica, &c. ; whilst the floating fruits 

 of more characteristic beach-trees like Barringtonia speciosa and 

 Cerbera Odollam, that grow also on the sides of the estuaries, were 

 never noticed in this condition. That this tendency should be 

 restricted to the plants of the mangrove-formation and is not to be 

 observed in the beach-trees is a singular fact. There is, however, 

 an intermediate group of littoral plants mostly belonging to 

 genera of the Leguminosee and Convolvulaceae, such as Mucuna 

 and Ipomea, where germination of the floating seed is apt to 

 begin but ends abortively, and results in the sinking and death of 

 the seed. The subject of the germination of seeds in the floating 

 drift of tropical estuaries presents itself, therefore, in three 

 aspects : — 



(i) As concerning the plants of the mangrove-formation, where, 

 excluding the viviparous species (when germination takes place on 

 the plant), germination is frequent in the water : 



(2) As concerning the beach-trees where it is rare or absent 

 altogether : 



(3) As concerning certain Leguminous and Convolvulaceous 



