238 PLANTS, SEEDS, AND CURRENTS 



lies a little below the zone of heavy rainfall ; but the climatic con- 

 ditions there are far more humid than on the coast beneath. This 

 distinction is important, because it is bound up with different degrees 

 of shrinkage of the coast and inland seeds, and with the consequent 

 different degrees of impermeability. As indicated below, the coast 

 seeds are smaller and lighter, contrasts which my observations on 

 seed-impermeability enable me to connect with a greater degree of 

 imperviousness resulting from more complete shrinkage of the seed- 

 coats. The coast seeds were 5-5 to 6 mm. in size and averaged 

 1-3 grains in weight; whilst the inland seeds measured 6-5 to 7 mm. 

 and had an average weight of 2 grains. 



The difference in behaviour is at once shown in an experiment 

 in sea-water commenced by me in Jamaica, continued there by 

 Mrs. H. B. Warde after I had left for England, and concluded by 

 me on my return to the island about half a year afterwards. Of the 

 coast seeds, 95 per cent, were afloat after seven and a half months, 

 and no more sank when the experiment was extended to nine months, 

 the seeds being still hard and sound. Of the inland seeds some 

 began to swell and sink after two months; but 60 per cent, were 

 afloat, and hard and sound, after seven and a half months. Some 

 of the sunken inland seeds germinated in the sea- water and plants 

 were raised from them. In another sea-water experiment carried 

 out by me in Jamaica the contrast in behaviour was greater. After 

 a month all the coast seeds were afloat in their normal state; but 

 several of the inland seeds began to swell in a few days, some of 

 them germinating in the sea- water, and only 10 per cent, remained 

 afloat in a hard, sound condition after a month. In a third sea- 

 water experiment conducted in England in the same year, under 

 warm conditions imitating those of the tropics, all the coast seeds 

 were afloat and normal after four months, whilst 69 per cent, of the 

 inland seeds alone floated ; the rest, having absorbed water, swelled 

 and sank. All the seeds employed in these experiments were of the 

 previous season's growth. It appeared in the course of this inquiry 

 that the " scar " was the place of weakness in the inland seeds as 

 regards the penetration of water. 



The seeds experimented upon were gathered from the well-dried 

 pods hanging on the coast and inland trees at the end of March 1907. 

 In both localities the previous year's pods were hanging in bunches 

 from the trees. In neither locality were the trees then in flower; 

 and whilst the coast plants were leafless, the inland trees displayed 

 abundant foliage, a contrast connected with the prevalence of more 

 humid conditions in the inland station. 



The bearing of these Jamaican experiments may be thus stated. 

 My experiments in the Pacific on the influence of an inland station 

 on the buoyancy of the seeds or fruits of typical shore plants were 

 concerned with plants that had extended miles inland in dry districts 

 where plants of the xerophilous habit prevailed. Here in Jamaica 

 we had typical shore plants invading the fringe of the lower forest 

 zone, where more humid conditions determined the hygrophilous 

 habit. The results obtained in Fiji and those obtained in Jamaica 

 are therefore in one sense not strictly comparable. In the first 



