GEOGRAPHICAL DISTRIBUTION. 39 



I suppose wherever there is sea, sea-weeds of some kind are 

 found. To a considerable extent, they seem to obey the 

 same laws as land-plants. Every zone presents a peculiar 

 system of vegetation. It is said that after a space of twenty- 

 four degrees of latitude, a nearly total change is produced 

 in the species of organized beings; this, it is thought, is 

 very much owing to temperature. It is very interesting to 

 observe the different appearances that Sea-weeds exhibit in 

 different seas, and also in different depths of the same sea. 

 How very dissimilar are Alg[E of the Arctic Seas from those 

 of Australia and New Zealand ! How remarkable are the 

 immense masses of floating Sea-weeds, such as those pro- 

 verbial wanderers the Sargassa, called also Gulf-weed ! 



Great accumulations of Sea-weed are found floating on 

 each side of the equator. The Mm- do Sargasso of the Por- 

 tuguese stretches between the 1 8th and 32nd parallels of 

 north latitude, and the 25th and 40th meridians of west 

 longitude. It is often called the Grassy Sea, for in it the 

 surface of the ocean, for several days^ sailing, is literally 

 covered with plants. Barrow mentions them in his 

 ' Yoyage to Cochin China '-, Humboldt also mentions them 

 in his ' Personal INJ'arrative.'* The most extensive bank is 

 near the Azores : vessels returning to Europe from Monte 



