66 Dansk Botanisk Arkiv, Bd. 2. Nr. 2. 



"vesicles thin, short-stalked, leaves thin, yellow-brown. Crypto- 

 stomata small, scattered. Receptacles very toothed". The recep- 

 tacles make it appear to be a well marked species". Judging 

 also from this I am inclined to think that Kützing's and 

 J. Agardh's plants do not belong to the same species, but to 

 decide this matter, much more material is necessary than I have 

 had at my disposal 1 ). 



') In this connection I wish also to point out here that I have had and 

 have now still more doubt as to how far it is justifiable to refer the 

 floating Sargassum from the Sargasso Sea (which I in my paper have 

 called S. Hystrix var. fluitans) to J. Agardh's species. When I refer- 

 red it to this plant it was — as I have pointed out in my paper — 

 because J. Agardh himself had already done so. As mentioned in my 

 paper quoted we have in the Botanical Museum here a specimen of 

 the floating form collected by Capt. Andrea in the Old Bahama 

 Channel I/VIII 1870 which J. Agardh has determined as Sargassum 

 Hystrix. This specimen is just like those I have collected in the Sar- 

 gasso Sea but both this one and also mine are decidedly different from 

 the fixed form collected by Liebmann; on the other hand it cannot be 

 denied that the fig. 1 of a sterile plant in J. Agardh's "Species Sar- 

 gassorum Australiæ", pi. VII shows much resemblance to the floating 

 form; it differs however in the almost entire absence of cryptostomata 1 ) 

 which are most often well-developed and numerous in the floating form 

 though occasionally leaves are found which quite or nearly lack them. 



That 1 considered the floating form different to the fixed I have 

 already shown in that I gave it the rank of variety. But with the 

 further knowledge I now have as to S. Hystrix I think it best to 

 consider var. fluitans as a proper species coordinate with S. natans. As to 

 the origin of S. fluitans, we have, just as is the case with S. natans 

 only supposition to go upon. It may be derived from S. Hystrix, but 

 it might equally well have had other parents. 



Herewith a short diagnosis: 



Sargassum fluitans nov. spec. 



Sargassum Hystrix J. Ag. var. fluitans Borgs. 1. c, p. 11, Fig. 8. 



Sargassum Hystrix J. Ag. ex parte. J. Agardh, Spec. Sargass. Austral., p. 91. 



Axis teretiusculus, ramosus, foliis lanceolatis vel linearibus, mar- 

 gine irregulariter dentato, distincte costatis, cryptostomatibus pro 

 ratione majoribus conspicuisque. Vesiculi numerosi, sphærici, magnitudi- 

 nem seminis pisi fere æquantes duplo longioribus quam pedicellis eorum. 



Long. fol. = ca. 25—30 mm ; lat. fol. = ca. 4—5 mm. 



Lat. vesic. = ca. 5—6 mm ; long, pedicell. vesic. = ca. 3 mm. 



] ) In the text to the plate J . Agardh says : cryptostomatibus nullis aut obsoletis instructa 



6X 1914. 



