MAEINE BOTANY. 117 



bearing a coronal of Dichotomous leaves, which, reach a 

 length of thirty and forty feet. Martins tells us that the 

 Sea Otter, when watching for its prey, likes to rest on the 

 air-vessels of these giants ; and that the tough long stems 

 supply the rude fishermen of those parts with excellent 

 lines. 



The growth of the Nereocystis must be extraordinarily 

 rapid; for it is an annual, is never seen in spring, and 

 therefore develops its enormous size in the course of a single 

 summer. 



Before we pass to the third great group of marine plants, 

 the Rhodosperrns, or Fucoids, we must refer to the enor- 

 mous weed meadows or fucus-banks of the Atlantic, which 

 are among the greatest marvels of the ocean. It is well 

 known that the mighty Gulf Stream, which pours its blue 

 masses of water from America to Europe, at the Azores 

 partly turns southward again towards the African coast, 

 and is driven back to the American coast by the north-east 

 trade-wind. Within this limit a sea is enclosed from 22 

 deg. to 36 deg. n.l., and from 25 deg. to 65 deg. w.l., 

 which displays very few currents, and those depending on 

 the wind blowing at the time. This quiet portion of the 

 ocean, whose surface is thrice as large as Europe, is found 

 to be covered with larger or smaller heaps of Sargassum 

 bacciferum. Some days it collects round the ship in such 

 masses, that its progress is impeded, while at other times 

 hours elapse before a plant is seen. "When Columbus 

 crossed this unknown Sargasso sea, his desponding com- 

 rades became still more apprehensive ; for they believed 

 that these floating beds of sea-weed, which hemmed the 

 course of their vessel, indicated the limits of the navigable 

 ocean. 



It deserves mentioning as an interesting fact, that these 

 fucus-banks afford us the most remarkable instance of gre- 

 garious plants of a single species. Nowhere else, neither on 

 the grassy prairies of America, nor in the heathe and forests 



