INTRODUCTION. XXI 



Hope, sometimes, in these latitudes, pass through immense 

 fields of sea-weed ; and others, though steering exactly the 

 same course, and at the same season, meet with scarcely any. 

 1 have made the voyage four times, and only once met with 

 sea-weed in sufficient quantity to claim any attention. It 

 did not then occur in strata resembling fields, but rather in 

 ridges, from ten to twenty yards broad and of great length, 

 stretched across the sea. The species invariably found in 

 these was S. bacciferum. Of a large quantity that we 

 dredged up for several successive days not a particle be- 

 longed to S. vulgare, and I am much inclined to suspect 

 that most, if not all, of the stories related by voyagers as of 

 that species, belong to *S". bacciferum, a plant which has 

 never been found in any other situation than floating about 

 in the deep sea, whereas S. vulgare (the Focus natans of 

 Turner) is well known in many tropical countries to grow 

 on the rocks, within the reach of the tide, like others of the 

 genus. It is therefore much to be regretted that the name 

 of natans was not retained for S. bacciferum, to which it is 

 chiefly, if not only, applicable. Authors who have written 

 on this Fucus have much disputed, both respecting its ori- 

 gin and whether it continues to grow whilst floating about. 

 Nothing at all bearing on the former question has yet been 

 discovered, for though species of Sargassum abound along 

 the shores of tropical countries, none exactly corresponds 

 with S. bacciferum. That the Ancestors of the present 

 banks have originally migrated from some fixed station is 

 probable, but farther than probability we can say nothing. 

 That it continues to flourish and grow in its present situa- 

 tion is most certain. Whoever has picked it up at sea, 

 and examined it with any common attention, must have 

 perceived not only that the plants were in vigorous life, 

 but that new fronds were continually pushing out from the 

 old, the limit being most clearly defined by the colour, 



