46o A NATURALIST IN THE PACIFIC chap. 



cent, float vertically or steeply inclined in fresh-water. The same 

 general rule applies to R. mangle, whether in the rivers and seas of 

 Fiji or in those of Ecuador. In those cases where the seedling 

 drops prematurely on account either of storms and floods or of the 

 depredations of a grub that frequently attacks the fruit, this rule 

 would not apply. One may frequently notice in Fiji after heavy 

 weather that seedlings detached prematurely, and often carrying 

 the fruit, are floating in numbers horizontally in the rivers. In a 

 few days, as a rule, the fruit-case becomes detached and sinks. 



It may be remarked that the horizontal position is much better 

 adapted for the safety of the seedling in transport than the vertical 

 position. In the last case the plumule, which protrudes above the 

 water, would be unable, as indicated in my experiments, to with- 

 stand the scorching rays of the sun in a smooth sea ; whereas in 

 the horizontal position, which the seedlings assume in sea-water, 

 the plumule is more or less completely submerged, and the risk of 

 withering in the sun is very much less. The Rhizophora seedlings 

 would certainly have little chance of crossing in safety a large tract 

 of sea, if they floated, as they do in river-water, with the plumule 

 exposed above the surface. It is not unlikely that the compara- 

 tively restricted area occupied by Rhizophora conjugata may be 

 due to the attitude its seedlings assume when floating in sea-water. 



The stranded seedlings of Rhizophora readily establish them- 

 selves for a while in very different situations ; and it is by no means 

 necessary that they should be washed ashore on a muddy coast. 

 When half-buried amongst the heap of vegetable drift piled up on 

 a sandy beach they are frequently to be found striking into the 

 sand and showing their first leaves. Here they ultimately perish 

 in the great majority of cases ; but when protected long enough to 

 jeach the moist sand four or five inches below, they may give rise 

 to a little mangrove colony. When caught in a fissure in the bare 

 reef-flats these plantlets are sometimes able to establish themselves. 

 Rhizophora seedlings would, however, require a coast prepared by 

 them by the work of ages before they could form extensive swamps. 

 It is, therefore, not surprising that Prof Penzig found no evi- 

 dence of mangrove-settlements on the shores of Krakatoa fourteen 

 years after the eruption. 



Yet suited as Rhizophora seedlings are for crossing tracts of sea, 

 I regard them as quite unfitted for being transported by the currents 

 unharmed across an ocean. The plumular bud is insufficiently 

 protected for such a long voyage of many months, and perhaps of 

 years. Though the horizontal position of the seedling would secure 



