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 Alge 
towards ocean currents, though the air-floats of 
Fucacee and Laminariacee, 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 
—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. 
