472 



ISLAND LIFE. 



[part II. 



— notably in the case of the Azores and Bermuda. The cha- 

 racter of the plants is also just what we should expect; for 

 about two-thirds of them belong to genera of world-wide range 

 in the temperate zones, such as Bammculics, Drosera, Uj^ilohium, 

 Gnaphalium, Senecio, Convolvulus, Atriplex, Luzula, and many 

 sedges and grasses, whose exceptionally wide distribution shows 

 that they possess exceptional powers of dispersal and vigour of 

 constitution, enabling them not only to reach distant countries, but 

 also to establish themselves there. Another set of plants belong 

 to especially Antarctic or south, temperate groups, such as Colo- 

 hrmthus, Accencc, GaultJicria, Perncttya, and Mulilenheclda, and 

 these may in some cases have reached both Australia and New 

 Zealand from some now submerged Antarctic island. Again, 

 about one-fourth of the whole are alpine plants, and these 

 possess two advantages as colonisers. Their lofty stations 

 place them in the best position to have their seeds carried away 

 by winds; and they would in this case reach a country which, 

 having derived the earlier portion of its flora from the side of 

 the tropics, would be likely to have its higher mountains and 

 favourable alpine stations to a great extent unoccupied, or 

 occupied by plants unable to compete with specially adapted 

 alpine groups. 



Fully one-third of the exclusively Australo-New Zealand species 

 belong to the two great orders of the sedges and the grasses ; 

 and there can be no doubt that these have great facilities for dis- 

 persion in a variety of ways. Their seeds, often enveloped in 

 chaffy glumes, would be carried long distances by storms of 

 wind, and even if finally dropped into the sea would have so 

 much less distance to reach the land by means of surface cur- 

 rents ; and Mr. Darwin's experiments show that even cultivated 

 oats germinated after 100 days' immersion in sea-water. Others 

 have hispid awns by which they would become attached to the 

 feathers of birds, and there is no doubt this is an effective mode 

 of dispersal. But a still more important point is, probably, that 

 these plants are generally, if not always, wind-fertilised, and 

 are thus independent of any peculiar insects, which might be 

 wanting in the new country. 



Why easily-dispersed plants have often restricted ranges. — 



