4: THE MARINE BOTANIST. 



Sarg'assum^ no species of which are indig*enous on 

 our coast^ we have four British genera inchided in 

 the Fucus tribe. The Sporochnacese are remark- 

 able for their deHcate fronds speedily changing- 

 colour and becoming flaccid on exposure to the 

 atmosphere. Six species comprised in four genera 

 are known on our shores^ of which the Desmarestiae 

 are alone frequent, and these, our three native 

 kinds, are widely dispersed through the Atlantic 

 and Pacific Oceans. In the next tribe of the 

 Laminarias are found sea-weeds, attaining- the 

 gi^eatest size of any vegetating in these seas, their 

 stems and fronds together often measure eighteen 

 feet in length, and the string-like Chorda frequently 

 has fronds forty feet long ; but it is on the shores 

 of the Pacific, along the north coast of America, 

 and for a greater distance, that an immense alg-a 

 of this tribe grows to the astonishing dimensions 

 of one thousand feet : large submerged meadows 

 are formed by this Macroscystis, so dense, that it 

 is with difiiculty ships will answer to the rudder 

 when steered through the mass ; and during the 



