I9I4.] FARLOW— VEGETATION OF SARGASSO SEA. 259 



a large genus, the largest of all the genera of the larger brown sea- 

 weeds, and includes mainly species which inhabit the tropics, or more 

 accurately between about 42° N. and 42° S. latitude. They flourish 

 just below low water mark but do not grow in deep water. They are 

 attached to the substratum by a hold-fast and grow not infrequently 

 to be three feet long, with a branching, slender stem bearing leaves 

 with small, stalked air-bladders near their bases. The fruit, the 

 spores, are in cavities on special branches. The genus is a difficult 

 one for the systematic botanist because, to be sure of a species, one 

 should have not only the stem with its leaves but also the base and 

 the fruit and in many cases species have been described from frag- 

 ments only. Furthermore the individuals of most species vary very 

 much so that, without a study of a set of living specimens, an 

 algologist might be pardoned for believing that he had not one but 

 several species before him, judging by herbarium specimens only. 

 The points I have just mentioned must be borne in mind in what I 

 have to say about the gulf-weed. It remains for us to consider the 

 two questions: What is the gulf-weed and where does it come from? 

 All observations agree that the masses of floating gulf-weed 

 consist in far the greater part of the single species, called Sargassum 

 bacciferum. If, however, we examine more closely the traditional 

 gulf -weed we find that although it has the characteristic leaves and 

 bladders of the genus, it has no remains of a basal attachment 

 and no fruit except in certain very rare and not well authenticated 

 cases. Some believing that, if not impossible, it is certainly very 

 improbable that any species could continue to flourish indefinitely 

 like the gulf-weed without at some time fruiting and, furthermore, 

 seeing a certain resemblance of the leaves and bladders to those of 

 certain species of Sargassum growing attached in the West Indies 

 and on the Florida coast, have advanced the opinion that the floating 

 form called gulf-weed consists of branches broken from the attached 

 forms and carried by the gulf stream to the different parts of the 

 Sargasso Sea. Others maintain that this is not the only case of a 

 plant living and flourishing without producing fruit, and that, since 

 up to the present time, no one has found the Sargassum bacciferum 

 attached and fruiting, we are forced to believe that it is a distinct 

 but always sterile species and not a form of any other attached 



