KONGL. SV. VET. AKADEMIENS HANDLINGAR. BAND. 20. \N: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 nutnerous 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 robust« and ramosa are in all probability not before unknown, no more 
than f. swbsitmplea and f. densa. For it does not appear doubtful to me that f. robusta 
is Lepecuin’s Lucus graminifolius figured in Comment. Petrop. pl. 23, and that f. ra- 
mosa is the same author’s Fucus tubulosus given in pl. 20. Gost is indeed of opinion 
that FP. graminifolius is a H. ramentaceum, but on the other hand he assumes Fucus 
tubulosus, which J. G. AGARpH and Ruprecur refer also to this species, to be Dumontia 
filtformis. Goxr rests this assumption on the resemblance that is to be seen between 
Lerecuin’s figure of Fucus tubulosus and Harvey's figure of Dumontia jiliformis in Phye. 
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 pl. 13, fig. 4, and which might almost be thought to 
be a copy of the above-mentioned figure by Lerecuin. However, there being still 
some uncertainty with respect to Lreprecuin’s two species of /’ucus and his names 
being moreover, in case these so-called Fuci are identical with the //alosaccia 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 flalosaccion ramentaceum f. robusta mihi to be most probably identical with Fucus 
graminifolius Lerrncn. and f. ramosa mihi with Fucus tubulosus Lerecn. 
Habitat. The form densa is litoral in the Norwegian Polar Sca, 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. rainosa @ major, probably also f. sub- 
simplex, 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 /? 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, 
