1917] Collins,— The Sargasso Sea 81 
be found scattered through the mass, on or near the shore, but there is 
no danger of a careful observer making any mistake. The plants of 
S. lendigerum and the other attached species are darker in color, never 
project above the Surface, and soon decay. 
S. fluitans I found scattered among S. natans all about Bermuda; 
at a rough estimate about five per cent of the former, ninety-five per 
cent of the latter. They are quite distinct, and in the large quantity 
of both species I examined, I found no intermediate forms. Indeed 
I found that when I had shown a specimen of each to our boatman, who 
knew nothing whatever of algae, he was able to distinguish in the 
floating mass the less common S. fluitans, and bring in with his boat- 
hook as much as I wanted, without once making a mistake. S. natans 
and S. fluitans, collected together in lat. 25.58 north, long. 73.39 west, 
were distributed in Collins, Holden & Setchell, Phyc. Bor.-Am., the 
former under No. 833 as S. bacciferum forma angustum Collins, the 
latter under No. 832b as S. bacciferum. It is unfortunate that of the 
two forms then passing under the name of S. bacciferum the one cor- 
responding to S. fluitans should have been taken as representing the 
type, and a form name given to the other, which we now know agrees 
with the Linnaean type.! 
It is not impossible that S. fluitans has been derived from S. Hystrix, 
but if so, it must be a somewhat remote derivation, and the modifica- 
tions have been sufficient to justify its rank as a distinct species. The 
derivation of S. natans is probably still more remote, the differentia- 
tion greater. Among the species known to me, the one that most 
resembles S. natans is one found at Bermuda resembling S. linifolium 
(Turn.) J. Ag., of the Mediterranean and the Adriatic. In the Ber- 
muda plants so referred the leaves are very long and slender, as in 
S. natans, and the vesicles are not unlike. That this plant has been 
reported, as far as I know, from no other American station, is not of 
much importance if we consider the pelagic form to have arisen long 
ago, and not now to receive any accessions from attached plants. 
That no floating form occurs in the Mediterranean, where S. linifolium 
is common, may suggest that the Bermuda plant, though resembling 
the Mediterranean species, is distinct; indeed I am still in doubt after 
examining a large number of specimens of the former, and comparing 
1 By a misprint in the label of No. 833, the latitude is given 55.58. Itis however, stated that 
the material was collected at the same time and place as that of No. 832, which has the correct 
figures of latitude, 25.58. 
