KONGL. SV. VET. AKADEMIENS HANDLINGAR. BAND. 20. N:0 5. 115 



lawa, I can no longer maintain this opinion. It is a high-arctic form, adapted to the 

 peculiar physical circumstances of the Polar Sea. My opinion of f. dadostephus « densa 

 I liave stated Spetsb. Thall. 1. p. 8, and I have found no reason to abandon it. But 

 låter observations have convinced me, that that plant from Spitzbergen which 1 once 

 determined as Rh. subfusca must be regarded as a form of Rh. lycopodioides. It is 

 allied with its f. dadostephus a densa, just as f. läxa of the typical form of the species 

 is allied with the subform // compacta. 



That these two forms are very nearly related, will be doubted by no one that 

 has had an opportunity of seeing a greater number of specimens of both of them. 

 They are connected by numerous intermediate forms. The elegant subform / tenera 

 is assuredly another vai'iety, of the same value as these. It is a Rh. lycopodioides f. typica, 

 that has grown in brackisk or almost fresh water. 



Hab. It is a priori probable, that a plant appearing in so niany different shapes 

 will present many diversities even in its habitat. This is indeed the case. Still it is 

 remarkable, that one form at least, although exposed to very different external con- 

 ditions, retains its characteristic appearance in a most noteworthy degree. I have al- 

 ready mentioned that this is the case with f. typica a congesta. There are specimens 

 of it, grown within the sublitoral zone on the west coast of Novaya Zemlya, that 

 cannot be distinguished from specimens grown on rocks between tide-marks on the coast 

 of Norway. It is also noticeable, that this form and the very nearly related Rh. 

 lycopodioides f. dadostephus cc densa are often niore luxuriant than the typical form 

 on the north coast of Norway. This is rather reduced in size, and generally keeps 

 about the length of 5 — 10 cm., scarcely ever reaching 15 cm. On the west coast of 

 Norway it becomes at least 25 cm. long, on the coast of Britain still larger, upwards 

 of 2 feet, according to Harvey. In order to give a clear idea of the habitat of this 

 plant, it will be most fit to treat of each form separately. 



Rh. lycopodioides f. typica. In the Norwegian Polar Sea, where this is the most 

 common form, it occurs almost always within the litoral zone, partly on rocks between 

 tide-marks, partly in tide-pools. In the former case, it always appears as « compacta, in 

 the latter as well as when descending rarely into the upper part of the sublitoral zone, it 

 sometimes, though far from always, has the aspect of (i läxa. When growing in places 

 where the saltness of the water is little, it invests itself with the peculiar habit of y tenera. 

 On the west coast of Greenland it is now litoral, now sublitoral. In the arctic region 

 proper of the Polar Sea, the plant is always sublitoral and belongs here to the formation 

 of Laininariaceas. It is properly a pelagic form; however it enters also into deep bays, 

 although, according to my experience, it is far more rare here than on unsheltered 

 coasts. In the Norwegian Polar Sea it is gregarious, but not in the Arctic Sea proper. 

 I have not seen specimens with sporocarpia from the Arctic Sea. Individuals bearing 

 tetrasporangia have been found on the coast of Norway in the months of June, July, 

 and August; on the west coast of Novaya Zeuilya I have found such specimens in July. 



Rh. lycopodioides f. cladoste])hus resembles the preceding form with respect to its 

 habitat, when it occurs within the arctic region of the Polar Sea. 



