MISCELLANEOUS PLANTS 



195 



one end of the stone, which in time would admit the gastric 

 fluids. 



My observations on the suitability of the fruits for transport by 

 currents were made in Jamaica on coast plants. The drupaceous 

 fruits are about an inch long, have a crustaceous fleshy covering, 

 and enclose a prominently ribbed stone (nearly as large as the entire 

 fruit), the walls of which are about 2 mm. thick. Inside is a single 

 seed which does not quite fill the cavity, and it is to this empty 

 space that the buoyancy of the dry fruit is due. But the seeds 

 often fail in a large number of fruits. In one locality I found that 

 only 10 per cent, were seeded. In the case of more or less empty 

 fruits there will usually be found the remains of two seeds, and 

 investigation showed that each of the two ovules, forming the ovular 

 complement of the genus, had developed into seeds, which, after 

 attaining a size of 3 or 4 mm., aborted and shrivelled up. Such empty 

 fruits, though useless for purposes of dispersal, are readily transported 

 by the currents 



The fruits in the form of the dry more or less bared stones rarely 

 occur in the Jamaican beach- drift, and when found are usually 

 empty. It was in this condition that I found most of the fruits 

 in the beach-drift of the Black River coast and of the coast near the 

 White River on the north side of the island. The fresh fruit floats 

 at first ; but I should not imagine that it would float for a long time, 

 unless the failure of both seeds had resulted in an empty seed-cavity. 

 The dried stones as they lie under the plants are much more buoyant. 

 Four of these selected stones, which had been gathered a few months, 

 were placed in sea-water After two months they were all afloat, 

 and of two cut open one proved to have a sound seed and the other 

 a rotting seed. I should greatly doubt, however, whether the 

 currents, where a period of flotation exceeding two or three months 

 is involved, would prove to be effective agents for the dispersal 

 across an ocean of any sound fruits. A canal, which at one end of 

 the stone leads into the seed-cavity, is merely filled with soft tissue 

 that would in time permit the penetration of sea- water, thus bringing 

 about the death of the seed. 



As regards dispersal by currents, the absence of this plant from 

 such a well-examined group of islands as the Bermudas is significant, 

 since so many West Indian strand plants have been carried there 

 through this agency. Nor can we appeal to the presence in the 

 Bermudas of its constant West Indian associate, Coccoloba uvifera, 

 since its indigenous character is doubtful, a matter referred to when 

 dealing with that plant. It is highly improbable that fruits with a 

 sound seed could ever cross the North Atlantic with the Gulf Stream 

 drift, though one might expect to find occasionally on the shores 

 of Europe an empty stone or one with the seed decayed. Nor could 

 the fruits withstand the six or eight months' immersion involved in 

 a passage to West Africa in the Counter Equatorial Current, even 

 if such a traverse was feasible. The chances that the currents could 

 carry the stone with a sound seed from the New World to tropical 

 West Africa may be thus ruled out. On the other hand, a capacity 

 of floating in the sea for two or three months without injury to the 



