18 PLANTS, SEEDS, AND CURRENTS 



Summary 



1. After remarking that beach-drift has much the same general 

 characters over the West Indian region, it is pointed out that its 

 principal sources are the plants of the beach, of the coastal and 

 estuarine mangrove swamps, and of the riverside in inland districts 



( P . i). 



2. Whilst the beaches near an estuary in a large island are the most 

 suitable localities for the drift in the mass, it is in the low islet lying 

 far out to sea that we find the best opportunity of investigating the 

 portion of it that is most fitted for oceanic transport. Such an islet 

 receives only the residue of a vast amount of vegetable debris which 

 for the most part soon goes to the bottom (p. 2). 



3. The distinction is drawn between local and foreign beach-drift, 

 the latter which is derived across the sea from other islands being 

 likely to be masked by the local materials (pp. 2, 3). 



4. As illustrating the part taken by rivers above the mangrove- 

 lined estuary in supplying drift to the beaches, the Black River of 

 Jamaica is taken as an example; and it is shown that on account 

 of the tendency to germinate when afloat many of the seeds and fruits 

 of riverside plants have little or no effective value for over-sea dis- 

 tribution (p. 3). In others again the floating power is either absent 

 or slight; whilst there may be cases where the buoyancy is great, 

 but the seeds have a fleeting vitality and soon decay. The con- 

 clusion is formed that not one-fifth of the seeds and fruits brought 

 down by a West Indian river from inland districts to the sea would 

 be capable of reproducing the plant after a traverse of a hundred 

 miles of ocean (pp. 4, 5). 



5. The mangrove formation as a source of drift is next discussed. 

 It is shown that whilst the true mangroves (Rhizophora, Laguncu- 

 laria, Avicennia) are in one form or another well adapted for over- 

 sea transport, in the case of their associates (Anona, Carapa, Manx- 

 caria, Sacoglottis, etc.) the floating seed or fruit has many difficulties 

 to contend with, which considerably restrict their capacities for 

 effective distribution by currents (pp. 4, 5). 



6. Then the plants of the beach-borders are dealt with from the 

 same standpoint, and a list is given of West Indian beach plants 

 commonly represented in the drift. It is remarked in passing that 

 in their much smaller size the fruits of West Indian beach trees offer 

 a great contrast to those of the trees of the far more luxuriant beach 

 vegetation of the tropical islands of the Indian and Pacific Oceans 

 (pp. 5, 6). 



7. The difficulty in discriminating between local and foreign drift 

 is again alluded to, and reference is made to the sorting out by the 

 waves of the finer and larger components of the beach-drift (p. 6). 



8. Whilst fresh emphasis is laid on the uniformity in general 

 characters of the beach-drift of the West Indian region, it is shown 

 that each locality may present some peculiar feature (p. 6). 



9. The author then refers to his method of identifying the con- 

 stituents of the drift (pp. 7, 8). 



10. The distribution over the West Indian region of the seeds and 



