KONGL. SV. VET. AKADEMIENS HANDLINGAR. BAND 20. N:0 5. 197 



Syn. 'Fucus serratus Kleen, Nordl. Alg. p. 25. 



» » Lyngb. Hydr. Dan. p. 5. 



» » Nyl. et Ssel. Herb. Feun. p. 73. 



» » Post et Rdpr. 111. Alg. p. II. 



» » Wg. F1. Lapp. p. 489. 



Remark on the definition of the forms. Being of the opiuion 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 may be grouped, I 

 have thought fit to call attention to the types of Fucus serratus described above. I 

 think that all the forms contained in the collections of Fucus 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 and the more densely serrate 

 upper segments. In both forms the frond is leathery when dried, with wineed 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. F. angusta is most closely allied to that form which 

 may be considered the proper glacial forms, namel}' 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 cosfce; the segments are short, with a few 

 shallow seri-atures on their curved margins and numerous cryptostomata. This is the 

 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 Laminariacece. It flourishes both in exposed and sheltered places of the coast; f. 

 grandifrons prefers, however, more quiet 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 



