54 
fucace^:. 
IV. 
Sar. bacciferum , but straggling specimens occur in the Pacific and Indian Oceans, 
and on the shores of Australia and New Zealand ; and some few, carried northward 
by the Gulf stream, reach the northern shores of Europe in safety. 
Naturalists have been puzzled to account for the origin of the Gulfweed, and 
formerly it was supposed to be altogether derived 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 fresh 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 different 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 delicate and of paler colour, and evidently in a young and sprouting state. 
Such a specimen is clearly in vigorous life, yet it has no root. But the absence of 
root is a matter of very trivial moment in a seaweed ; for we must bear in mind 
that the roots of Algse 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 dispensed with. No doubt the specimen under examination originated 
in a little 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, there- 
fore, no growth from spores. The supply of plants is consequently kept up and 
extended by the constant development of buds or gemrnce, originating in broken 
fragments of branches. I have taken some pains to examine numerous specimens, 
picked up on various parts of the bank, while fresh from the sea, and have in 
general been able to convince myself that the tuft under examination had origi- 
nated 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 first 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 immense bank from which the supply of Sargassum is 
constantly derived ; but such a bank, if covered by only as much water as the 
greatest depth at which any Fucaceous plant is known to grow, could scarcely have 
escaped the notice of voyagers. And the aspect of this Sargassum , with its innu- 
merable floating-bladders, shews that it was not intended to vegetate at any great 
depth ; for we invariably find the air-vessels most numerous in species which rise 
to the surface, and altogether absent in those which are deeply submerged. 
