KONGL. SV. VET. AKADEMIENS HANDLINGAR. BAND 20. N:0 5. 197 
Syn. Fucus serratus Kieun, Nordl. Alg. p. 25. 
» » Lynas. Hydr. Dan. p. 5. 
» » Nyl. et Sel. Herb. Fenn. p. 73. 
» » Posr et Rupr. Ill. Alg. p. IL. 
» » We. FI. Lapp. p- 489. 
Remark on the definition of the forms. Being of the opinion that the directions and 
limits of the variations of a very variable species are less sharply and distinctly brought 
into view by giving a general description comprising all the forms, than by establishing 
and characterizing certain typical forms, round which the others inay be grouped, I 
have thought fit to call attention to the types of Fucus serratus described above. | 
think that all the forms contained in the collections of Mucus serratus from the Polar Sea 
may be pretty easily and naturally arranged round these types. I have set down as 
the typical Fucus serratus the form delineated by Harvey in Phyc. Brit. tab. 47, which 
occurs commonly on the west coast of Sweden and also on the arctic coast of Norway. 
Near this there stands a form, called by me f. angusta, which has been found within 
the arctic region of the Polar Sea in the eastern part of the Murman Sea. It differs 
from the typical form by the considerably slenderer frond aud the more densely serrate 
upper segments. In both forms the frond is leathery when dried, with winged segments 
of five or more orders. The segments, both the sterile and the fertile, are linear or 
wedge-shaped, with almost straight contour and truncate tips. The cryptostomata are 
pretty numerous and distinct. I. angusta is most closely allied to that form which 
may be considered the proper glacial forms, namely f. arctica J. G. AG. This has 
somewhat shorter segments, of a less firm consistency and with the tips more rounded, and 
few or no cryptostomata. Then there is a peculiar form, approaching the former, which 
KLEEN has found growing in rock-pools at Nordlanden, f. abbreviata. It has all the 
segments, except the ultimate, reduced to costw; the segments are short, with a few 
shallow serratures on their curved margins and numerous cryptostomata. This is thie 
smallest of all the forms, probably becoming only 15—20 cm. high. That form which 
I have named f. grandifrons possesses the largest dimensions of all. In this, as in f. 
abbreviata, only the segments of the last order are winged with curved margins and 
roundly truncate tips, and all the segments are short, particularly the upper ones which 
bear receptacles; but it differs by its more considerable size, especially in breadth, and 
by the upper segments being sharply and profoundly serrate. 
Habitat. The species is generally litoral in the Norwegian Polar Sea, growing 
(f. typica and f. angusta) in the lower part of this zone, or (f. abbreviata) in rock-pools 
between tides. Sometimes (f. grandifrons) it descends into the upper part of the sub- 
litoral zone. On the coast of Novaya Zemlya and probably also at Spitzbergen (f. an- 
gusta and f. arctica) it occurs in the sublitoral zone as an element of the formation 
of Laminariacee. It flourishes both in exposed and sheltered places of the coast; f. 
grandifrons prefers, however, more quict localities. The typical form is gregarious, but 
of the others a few scattered individuals only are found to grow in the same place. 
The typical form and f. grandifrons are furnished with receptacles from July to the 
beginning of October on the north coast of Norway, f. angusta has been found with 
