1 62 Transactions. — Bota ny. 



There are three principal ways hy which the seeds of plants 

 can be carried across wide spaces of ocean : by wind, by ocean 

 currents, and by birds. The first mode is chiefly applicable in 

 the case of the spores of ferns and cryptogamic plants generally ; 

 and it is no doubt through it that ferns constitute such a large 

 proportion of the flora of almost all oceanic islands. But with 

 respect to flowering plants, its importance is, I think, very much 

 over-rated. Had it operated to any extent, plants possessing 

 light seeds, or seeds furnished with winged appendages or down 

 (pappus), would be common on most oceanic islands. But this 

 does not always happen, and is certainly not the case with the 

 Kermadec Group. Distribution by means of ocean currents is 

 a more promising mode, and it can be shown to be a likely one 

 in the case of the Kermadec Group. It is well-known that in 

 the whole of the southern portion of the South Pacific the drift 

 of the ocean is to the north, forming what is called the ant- 

 arctic drift current. This current hugs both shores of New 

 Zealand, and extends to the North Cape ; but is usually said to 

 disappear about latitude 34°, and to be succeeded by a broad 

 expanse of ocean in which the currents are variable or hardly 

 perceptible. But in examining the shores of Sunday Island Mr. 

 Smith and myself were surprised to find numerous kauri logs, 

 evidently drifted from New Zealand. Mr. Bell informed us that 

 over forty were lying stranded on the beaches, and from what I 

 saw myself I do not think his estimate is much above the mark. 

 The logs bore brands of different dates, and, apart from that, 

 it was evident from their appearance that they had arrived at 

 different periods, so that it cannot be assumed that a specially 

 favourable gale, or temporary current, had drifted over a batch 

 that had made its escape from some of our timber-mills. Pro- 

 bably the antarctic current extends further to the north in this 

 portion of the Pacific than has hitherto been supposed. But if 

 logs are regularly drifted across, so may seeds, branches of trees 

 bearing seed-vessels, and vegetable debris of all kinds. Many 

 seeds are capable of germination after a prolonged submersion 

 in salt water. Mr. Darwin proved by actual experiment that 

 some retained their vitality after an immersion of over 100 

 days ; and M. Gustave Thuret has succeeded in getting the 

 seeds of nine species to germinate after being floated for thirteen 

 months in a vessel of salt water. Even in 100 days the branch 

 of a tree bearing ripe seed-vessels might be iloated across a 

 distance even greater than that separating New Zealand from 

 Sunday Island. Dispersal through the agency of birds might 

 also be the means of stocking the Kermadec Islands with some 

 plants. Most of the birds found in the group are New Zealand 

 species ; and in the case of sea-birds, such as the various 

 species of albatrosses and petrels, which possess immense 

 powers of flight and range over large distances of ocean, yearly 



