182 PLANTS, SEEDS, AND CURRENTS 



World, as well as on those of the West Coast of Africa. There will 

 be no necessity to discuss here the station of this tree in the outer 

 zone of the mangrove swamp, and I will limit my remarks here 

 to the part played by the young seedlings, on being freed from the 

 fruit coverings, in distributing the plant. 



In my book on Plant Dispersal (p. 489) mention is made of the 

 abundance of these seedlings in the lower course of the Guayaquil 

 River in Ecuador, and of their being carried out to sea and stranded 

 in numbers on the coasts near the estuary. Germination com- 

 mences on the tree, and it is in this condition that the fruit 

 usually falls into the water of an estuary. There it floats, and 

 the seedling soon frees itself from its envelopes and floats away. 

 The germinating fruits were to be observed in numbers thrown up 

 on the beaches of Jamaica, Trinidad, Tobago, etc. It is important 

 to note in this connection that sea- water is not injurious either to 

 the germinating fruit or to the freed seedling, and that the seedling 

 could be transported for considerable distances unharmed in the 

 sea. It has been shown by Dr. Millspaugh that with the two ether 

 mangroves, Rhizophora mangle and Laguncularia racemosa, Avicennia 

 nitida is one of the earliest plants to establish itself on the Florida 

 sand-keys. All three mangroves have made their home in the 

 Bermudas. 



The germinating fruit and the freed seedling might retain their 

 vitality a considerable time after being stranded on a beach. In 

 Jamaica I took five fruits on the point of falling from the tree. 

 They were on the eve of rupturing, and I inferred from the con- 

 dition of other fruits in the same stage that each of them contained 

 a dark-green, well-developed seedling. They were allowed to dry 

 in a room, with occasional exposure in the sun, for twenty-five days, 

 during which period three of them opened. They were then placed 

 in fresh- water, and within a week two of them were growing healthily, 

 notwithstanding that they had lost just 50 per cent, of their weight 

 in the drying process. 



Avicennia seedlings offer the only means of the dispersal of the 

 plant by currents, and although considerable tracts of ocean might 

 be safely crossed in this manner, it is not at all probable that they 

 could accomplish unharmed the long transatlantic passage in Gulf 

 Stream drift from the New to the Old World. On the other hand, 

 they seem sufficiently hardy to survive the much shorter passage 

 of from two and a half to three months in the Main Equatorial Current 

 from the west coast of Africa to Brazil. Avicennia is regarded as 

 an Asiatic genus, and according to this view the borrowing of its 

 species from the Old W T orld by way of the West Coast of Africa would 

 be quite consistent. As regards the time occupied in the traverse 

 in the Main Equatorial Current, it would be similar to that taken 

 up in the passage from the Florida region to the Bermudas, namely,, 

 two to three months, a passage that Avicennia seedlings must have 

 once safely performed previous to the establishment of this mangrove 

 on those islands. (See Note 14 of the Appendix respecting Bermuda 

 bottle-drift.) 



