10 SEAWEEDS 



which conveys sometimes salt-water and sometimes 

 fresh. 



The ocean currents are of primary importance as 

 agents of distribution, not only as streams of stable 

 temperature, but as vehicles of transport. Currents 

 of air and of water are justly regarded as potent 

 means of dispersal of land plants, and their efficacy in 

 this respect is the result of special adaptation on the 

 part of the plant, such as winged seeds, &c. No 

 such adaptations are called for in the case of Algas 

 towards ocean currents, though the air-floats of 

 Fucacecc and Laminar iaccce, which secure a buoyancy 

 in the first place for vegetative purposes, probably 

 serve in certain cases the end of distribution as well, 

 particularly in the gulf-weeds. As examples of the 

 influence of currents there may be cited the differences 

 in the marine flora between the east and west coasts 

 of South Africa the west under the influence of a 

 cold stream from the south, and the east affected by 

 the warm Mozambique current from the north ; again, 

 the marine flora of Bermuda in the track of the Gulf 

 Stream the most northern coral island in the world 

 r-is much more markedly West Indian than the 

 North American coast flora under the same parallel, 

 outside the influence of this current ; and, to trace the 

 Gulf Stream further on its path, there may be noted 

 the contrast between the characteristically temperate 

 marine flora of the Shetland Islands and the Arctic 

 flora of Cape Farewell in the same parallel, but sub- 

 ject to the cold East Greenland current. If the 

 matter were less obvious the proof of it could be 

 reinforced with numerous other instances. 



