158 PLANTS, SEEDS, AND CURRENTS 



the normal constituents of West Indian beach-drift. I found no 

 reference to their occurrence in European beach-drift ; but, as stated 

 below, they came under my notice amongst the foreign drift of the 

 Azores. 



The modes of dispersal now merit our attention. Although the 

 fleshy pericarp of the fruits might attract birds, the seeds in their 

 hard shells being apparently well able to withstand transport in a 

 pigeon's crop without injury, there is no evidence at my disposal 

 that frugivorous birds distribute the seeds. On the other hand, the 

 indications of West Indian beach- drift and the stranding of the seeds 

 in a germinable condition on the shores of Bermuda point unmis- 

 takably to the agency of the currents. Hemsley's view that the 

 seeds are dispersed by the currents (Chall. Bot., I., 43, 48; II., 27; 

 IV., 304) is thus well founded, and the behaviour of the seeds under 

 experiment in part confirms his opinion. 



The seeds are black, round, 10 or 11 mm. in diameter, and 

 have a hard, impervious shell about 1 mm. thick. The buoyancy 

 is of the type characteristic of convolvulaceous seeds, neither the 

 shell nor the kernel possessing any floating power of themselves, the 

 buoyancy arising from the fact that the kernel incompletely fills 

 the seed-cavity. When, however, the cavity is entirely occupied, the 

 seed sinks. Thus it happened that in my experiments in Jamaica 

 about half of the seeds sank at once in sea-water, and about three- 

 fourths of them sank in fresh-water. Of those that floated in sea- 

 water about half floated after a month's immersion, and 20 or 25 

 per cent, after six to seven weeks, some of the last being sound, 

 whilst in others it was evident that water was beginning to penetrate 

 the coverings. The weak spot in the hard shell is in the " scar," 

 the umbilical aperture previously closed tending to become patent 

 after prolonged immersion. Water finds its way slowly into the 

 interior, the hard shell softens so that it can be readily cut with a 

 knife, the kernel decays, and the seed sinks. When several seeds 

 are kept in the same vessel the water has to be changed frequently, 

 as the rotting kernels of the seeds that are absorbing water turn it 

 putrid. 



I would imagine that few seeds would display sound kernels after 

 more than two months in sea-water. This period, however, might 

 be sufficient for the transport of some of the seeds in a sound con- 

 dition to Bermuda from the Florida Strait; but it would be in- 

 sufficient for their passage to the Azores, for which several months 

 would be necessary (see Notes 12 and 14 of the Appendix). Though, 

 as far as I know, the seeds have not been found on European beaches, 

 their occurrence on the beaches of the Western Azores points, in 

 spite of the results of my experiments, to this possibility. I picked 

 up two seeds, both seemingly sound, one at Porto Pym in Fayal, and 

 the other near Magdalena at the west end of Pico. But even the 

 presence of these drift seeds in the Azores is inconsistent with the 

 indications of the experiments. Additional investigations are needed 

 before one can credit these seeds with the capacity of reaching isolated 

 islands like Easter Island through the agency of the currents. 



