KONGL. SV. VET. AKADEMIENS HANDLINGAR. BAND. 20. X:0 5. 155 



most known form, f. densa, were so essentially different from each other that they 

 ought to be regarded as distinct species, still they are connected by numerous inter- 

 mediate forms. 



I have based the determination of the forms on the first year's plant, because it is 

 in the first year, i. e. at the first time when the plants bear the prolifications producing 

 tetrasporangia, that the difference between them comes out most sharply. These proli- 

 fications having for the greatest part fallen off and new, shorter ones being developed 

 from the remaining stumps, especially the forms robusta and ramosa become very like 

 f. densa in habit. 



Besides the branching and the size and shape of the prolifications, there are other 

 differences in colour and consistency between these forms, but these characteristics are 

 found to change in the same individual at different stages of its development. It may 

 be stated in general that f. densa is more cartilaginous than the others and that the 

 prolifications in f. robusta are almost membranaceous, so that in drying they fall together 

 and become flat. Younger individuals are more intensely coloured than older ones 

 and pelagic forms more so than such as have grown in sheltered places. 



The forms robusta and ramosa are in all probability not before unknown, no more 

 than f. subsimplex and f. densa. For it does not appear doubtful to me that f. robusta 

 is Lepechin's Fucus graminifolius figured in Comment. Petrop. pi. 23, and that f. ra- 

 mosa is the same author's Fucus tubulosus given in pi. 20. Gobi is indeed of opinion 

 that F. graminifolius is a H. ramentaceum, but on the other hand he assumes Fucus 

 tubulosus, which J. G. Agaedh and Rdpeecht refer also to this species, to be Dumontia 

 filiformis. Gobi rests this assumption on the resemblance that is to be seen between 

 Lepechin's figure of Fucus tubulosus and Harvey's figure oi Duriiontia filiformis in Phyc. 

 Brit. It is easily perceived that the strength of this demonstration is considerably weakened 

 by that figure of what is assuredly a specimen of Halosaccion ramentaceum from Spitz- 

 bergen which I have given in pi. 13, fig. 4, and which might almost be thought to 

 be a copy of the above-mentioned figure by Lepechin. However, there being still 

 some uncertainty with respect to Lepechin's two species of Fucus and his names 

 being moreover, in case these so-called Fuel are identical with the Halosaccia in 

 question, unsuitable and misleading, because the leaves in neither of them are flat and 

 resemble the leaves of grasses, but are tubulous in both, although the wall has a more 

 solid structure in the one than in the other, I have thought fit to choose new names 

 for the forms now distinguished, stating however expressly at the same time that I 

 hold Halosaccion ramentaceum f. robusta mihi to be most probably identical with Fucus 

 graminifolius Lepech. and f. ramosa mihi with Fuctis tubulosus Lepech. 



Habitat. The form densa is litoral in the Norwegian Polar Sea, but in the other 

 parts of the Arctic Sea it is, like the other forms of the present species, sublitoral, as 

 far as my experience goes. Forma robusta and f. ramosa cc major, probably also f. sub- 

 simpleic, may be regarded as chiefly pelagic; even f. densa is most richly developed on 

 exposed coasts, although it enters also into deep bays; f. ramosa [i minor, on the con- 

 trary, prefers sheltered places, being most typically developed in bays with a loose 

 bottom consisting of pebbles and small stones. It keeps generally in shallow water, 



