F. Børgesen: The Species of Sargassum. 15 



Be it considered, at last, that the floating Sargassum as mentioned above is as 

 it seems always in active grovvth, I take it for granted that theGulfweed is peren- 

 nial, that it lives and dies out at the Sea. 



That this explanation is not entirely new, may be seen from Harvey's "Nereis 

 Boreali-Americana", part I, 1851, p. 54, where the illustrious English algologist has 

 expressed the same opinion; the observation of this author containing so much of 

 interest in this respect and being seemingly not much known, I take the opportunity 

 to give the quotation as follows: 



"Naturalists have beeu puzzled to acoount for the origin of the Gulfweed, and formerly 

 it was supposed to be altogether deri ved from the Gulf of Mexico; being torn off the shores 

 of the Florida reefs and keys, and carried to sea with the great current. It is possible (and 

 indeed probable) that the origin of the present floating banks may have been partly of this 

 nature, but it is most certain that the great masses of the weed that are at present found 

 floating have had no such immediate parentage, but are produced on the surface of the ocean 

 on which they float. Whoever has picked up the plant at sea, on any genuine portion of the 

 bank, must have seen that it was in a perfectly fresli and growing state, and if he have 

 looked at his specimen carefully, he will probably have observed, that different parts of the 

 same specimen were of very difierent ages; that though there was no apparent root, yet that 

 toward the centre of the mass a small portion of stem was of a much darker colour than the 

 rest, and possibly covered by parasitic incrustations; and that all the branches springing from 

 this central piece were successively more and more deHcate and of paler colour, and evidently 

 in a young and sprouting state. Such a Specimen is clearly in vigorous hfe, yet it has no 

 root. But the absence of root is a matter of very trivial moment in a sea weed; for we must 

 bear in mind that the roots of Algæ are merely holdfasts, intended to keep them from being 

 washed off the rocks on which they grow. And in a plant capable of enduring extensive change 

 of place, like this Sargassum, the root is the part which may be most readily expensed with. 

 No doubt the specimen under examination originated in a httle branch accidentally broken 

 from a neighbouring mass, and which being thus cast adrift, continued to push out new branches 

 and leaves. In this manner, by the continual breaking up of old fronds and the continued 

 growth of their broken parts, the floating masses spread over the surface of the sea. 



In this floating state the species never forms proper fructification. There is, therefore, no 

 growth from spores. The supply of piants is consequently kept ujj and extended by the con- 

 stant development of buds or gemmæ, originating in broken fragments of branches. I have 

 takeu some jjains to examine numerous specimens, picked up on various parts of the bank, 

 while fresh from sea, and have in general been able to convince myself that the tuft under 

 examination had originated in a fragment of an older tuft. 



This process of growth by breakage must have gone on for ages; from that early time 

 when the fiist individuals were brought from some unknown rocks by the currents of the 

 ocean. Humboldt indeed conjectures that between the parallels of 20° and 45° there is an 



know, at least, that other algæ in a more or less fragmentary condition, and occurring as ioose 

 masses are able to persist by means of vegetative reproduction. A fuller account conceniing this 

 matter will be given in the subsequent pages. 



