THE MARINE ALGÆ OF DENMARK CONTRIBUTIONS TO THEIR NATURAL HISTORY PART III RHODOPHYCEÆ III. (CERAMIALES) BY L. KOLDERUP ROSENVINGE WITH THREE PLATES D. Kgl. Danske Vidensk. Selsk. Skrifter, 7. Række, naturvidensk. og mathem. Afd., VU. 3 -»<>SH*fs:c>-.<- KØBENHAVN BIANCO LUNOS BOGTRYKKERI 1923-24 INTRODUCTION w3ince the fii'st part of this puhhcation was issued I have studied the marine Algæ on tlie Danisli coasts almost cverj' summer. During the last two years ni}' in- vestigations have been more extensive. This is chiefly due to the addition made to the area of the Danish flora in consequence of the reunion of North Slesvig with Denmark in 1920. The boundary on the eastern side of Slesvig having been removed from Heilsminde to Krusaa in the interior of Flensborg Fiord, the Little Belt area (Lb) has been augmented by the waters between Heilsminde in the north, and Sønder- borg and Pøl at the south-eastern extremity of Als, while the line bounding the Da- nish part of the Baltic (Bw) on the south must now be drawn from Krusaa through the middle of Flensborg Fiord and thence south of Bredgrund south of Als. Though these waters have formerly been examined by Professor Reinke, and their flora and vegetation dealt with in his well-known work Algenflora der westlichen Ostsee Deut- schen Anteils, 1889, I have considered it necessary to study the same waters myself. By the kindness of the fisheries director, Mr. F. V. Mortensen, T have been enabled, with the assistance of the fishery control motor-boat, to make investigations and collections in the waters round Sønderborg in June 1921, and in June 1922 to make similar investigations while onboard the control steamer S. S. Falken (fisheries super- visor Trolle Thomsen), along the entire eastern coast of South Jutland and likewise in the waters surrounding Funen. In both cases the material was collected partly, by means of a boat, from stone reefs and in other localities such as breakwaters near land, partly by dredgings from ship at a greater distance from land. In the autumn of 1922 there further occurred an exceptional oppoi'tunity to make dredgings in the North Sea and the Skagerak in places otherwise very difficult of access, since the marine research ship S. S. Dana was to make fishery investigations in these waters, and especiallj^ in places where one might expect to find Algæ. The Marine Research Committee very readily granted me room onboard, and the leader of the cruise. Dr. A. C. Johansen, did everything in his power to further my investigations. As I was obliged to break off my stay onboard on October 7th, mag. sc. Mr. C. A. Jørgensen was deputed to carry on my investigations of the flora of the Skagerak and the northern and central parts of the Kattegat until the cruise came to an end on October 19th. Mag. Jørgensen has later, in June 1923, made investigations onboard the Dana in the waters around Bornholm and left the collected Algæ at my disposal. 37* 288 In continuation of the list given on p. 22 et seq. I give below a list of the new dredging stations arranged on the same principles as the one already mentioned. 6"-^'l3.E.f.Grw. Most of the new dredging places are marked on the charts given on pp. 288 and 290. In the later those places at the shores where investigations and collections have been made are likewise indicated by a mark together with the name of the 289 place concerned. In deep waters the collections have always been made with a dredge where nothing else is indicated. In most other places an otter trawl has been employed. As the markings on the charts and in the list show, there was no vegetation at all in the southern part of the North Sea area even where the bottom was stony. This agrees with what earlier German investigations have shown "^ and what I myself found in 1905 at Horns Reef (Part I p. 22, Chart II). Further it was in accordance with what Dr. Johansen had found immediately before my arrival onboard the Dana. In thirty localities between 6°07' and 8°16' E. and between 55°00' and 56'08' N. on lishing with otter trawl no vegetation at all was found. It was confirmed, then, by these investigations that this part of the North Sea is a veritable desert as regards bottom vegetation. In the northern part of the North Sea area, where there were stones or at any rate gravel in nearly all the localities examined, the bottom was almost equally bare, being either entirely destitute of vegetation or showing only very sparse vegetation. This result maj% however, be partly due to the late season (the latter part of September) for I have formerly found a fairly abundant flora in some parts of this area at the close of July. In the Skagerak, too, the vegetation is on the whole very poor even on stonv' bottom, and only in a few places, mostly near land, do we find spots with continuous vegetation, especially at Hirshals, but also at Hanst- holm, Bragerne and Lønstrup. On the other hand, in the Skagerak one often comes across loose, drifting Algæ carried along by the strong current. On groins and breakwaters in the northern part of the North Sea area there is an abundant and fairly varied vegetation. At Fanø and Esbjerg the corresponding vegetation is poor in species and, according to Reinbold ^ and Jaap,^ the same is the case with the Algæ vegetation on the coasts of Rømø and on the west coasts of North Slesvig; I myself had no opportunity to examine Romo until August 1923. In the shallow sea between North Slesvig and the islands Zostera marina and Z. nana grow in low water, but there seem to be no Algæ. Mag. R. Sp.\rck who made dred- gings along the east coast of Fanø at a depth of 4—5 m. has kindly informed me that he got numerous oyster shells and mussel shells and not a few stones in the dredge, but that there was no Algæ vegetation. Only a little loose Fucus vesiculosus without vesicles and some Zostera got into the dredge. The waters washing the eastern coast of North Slesvig are so similar in char- acter to the adjoining parts of the Little Belt and the western part of the Baltic dealt with in Part I, that they do not require further mention here, the more so since they have been treated in Reinke's above cited w^ork. The depth conditions are shown on Chart II and in map p. 290. ^ J. Reinke, Notiz über die Vegetationsverhältnisse in der deutsclien Bucht der Nordsee. Bericht deut. bot. Ges. 1889 p. 367. Th. Reinbold, Untersuchung des Borkum-Riffgrundes. Sechster Bericht d. Komm. z. wiss. Unters, d. deutsch. Meere. III Heft. - Th. Reinbold, Bericht über die im Juni 1892 ausgeführte botan. Untersuch, einiger Distrilite der Sclileswig-Holsteinischen Nordseeküste. Sechster Bericht d. Komm. z. wiss. Unters, d. deutsch. Meere. lü Heft. ^ 0. Jaap, Zur Kr3ptogamenflora d. nordfriesischen Insel Rom. Schrift, d. Naturv. Vereins d. Prov. Schleswig-Holstein Bd. 12. 1902. 290 291 List of new dredging stations arranged according to the different waters. The localities are designated by letters like the foregoing ones (eoiii|). pji. 22— r)4). Some of the dredgings of the later years have been made by Dr. Henning Petersün, Mag. P. Kramp or Mr. J. Boye Petersen while I have examined the collected material of Algæ. The dredging stations of Mag. Jørgensen in October 1922 have been designed with the station ligures of the S. S. Dana. North Sea. (Ns) dU. (Dana St. 2835). "/,, 22. 4 miles N. 'U E- of Blaavandshuk light-house. 8 m. — Fine sand. — No vegetation. (Otter trawl). dV. (Dana St. 2836). 11 miles S. by W. of LyngTig light-house. 15 m. — Fine sand. — No vegetation. eG. (Dana St. 2846). '»/g 22. 9 miles S.W. Vz N. of Bovbjerg light-house. 24 m. — Gravel, stones. — No Algæ, only a fragment of Desmar. acul. eH. (Dana St. 2848). »79 22. 14 miles W. by S. V4 S. of Bovbjerg light-house. 27 m. — Sand with few stones. — No vegetation, el. (Dana St. 2849). »%22. 21 miles W. of Bovbjerg light-house. 34 m. — Clay with stones, shells. — No Algæ. eK. (Dana St. 2850). Vio 22. Lille Fiskebanke. 46 miles W. by N. of Bovbjerg light-house. 37 m. — Clay, large stones. Scarce Hildenbrandia protoiypiis. eL. (Dana St. 2851). Vio 22. Lille Fiskebanke. 53 miles W.N.W. V4 W. of Bovbjerg light-house. 37 m. — Coarse sand mixed with ooze, with shells. — No Algæ. eF. (Dana St. 2845). ^"1, 22. 2,5 miles W. by N. of Bovbjerg light-house. 18—22 m. — Sand, stones, claj'. — No vegetation ; only Rhodochorion meinbranaceiim in Hydrallmannia falcata. eE. (Dana St. 2844). "/,, 22. 12 miles N.W. by N. of Bovbjerg light-house. 26 m. — Gravel, stones. — Scarce Desmareslia aculeaia, otherwise onlj' incrusting Algæ (Lithoderma). dY. (Dana St. 2838). -^U 22. 10 miles S.W. V4 S. of Lodbjerg light-honse. 18 m. — Clay with single stones. — No vegetation. dX. (Dana St. 2837). =73 22. 11 miles W.S.W. V2 W. of Lodbjerg light-house. 28 m. — Fine sand. — No vegetation. eD. (Dana St. 2843). =79 22. S.E. of Jydske Rev. 22 miles W. of Lodbjerg light-house. 41 m. — Sand, gravel, stones. — No vegetation; only single specimens of Desmarestia aciileata and fragments of a few other Algæ. eN. (Dp.'-. St. 2853). Vio 22.