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26 MATS WlERNRich in species. ScatteredLaminaria saccharina(4) Belt of Rhodomelaceaewith ascidians, 10-17 m(upper part with Delesseriasanguinea). Polysiphoniaelongata, P. nigrescens,Rhodomela virgata( 5) Phycodrys sinuosa belt,17-25 mKATTEGAT, Swedish sideLower part with Corellaand Delesseria sanguineaKJELLMAN 1903; KYLIN 1907, pp. 231, 233, 234;SJOSTEDT 1927; HYLMO 1933; LEVRING 1935.Fucus serratus belt down to ea. 5 m. Furcellariabelt (sometimes beginning already at 2-3 m, mixedwith F. serratus) down to 12-15 m. Delesseria-Phycodrysbelt down to 18-20 m. Further down clay withshells and several red algae, ending at 25 m.From southernmost Kattegat is reported a similarbottom with Rhodomelaceae and Odonthalia dentata(KJELLMAN 1903, p. 73). According to KYLIN Laminariadigitata and L. saccharina are reduced in sizeand occurrence.Laminaria hyperborea, with accompanying redalgae, may still be found on deep-water shallows: outsidethe Kungsbacka Fjord, at 10-15 m (SuNESON1939, p. 752); Fladen; Store Middelgrund 10 m, halfwaybetween Anholt and Kullen (KoLDERUP ROSEN­VINGE 1924, p. 294; S0REN LUND 1947, p. 94).0RESUNDSJOSTEDT 1923, 1928; LONNBERG 1898.(1) Upper infralittoral.Northern entrance: Fucus serratus belt, except invery exposed positions, begins at low-water line.(Lower border unlmown.)Further south in the Sound in the central part andsouth of the threshold a Fucus vesiculosus belt withupper facies, It m broad, consisting of Ceramiumtenuicorne (?), grows between low water and 5 m.This is the beginning of the Baltic Fucus vesiculosusbelt, entirely infralittoral. Fucus serratus leaves the ·upper of the infralittoral and grows at 5- 10 m.(2) Lower infralittoral on certain shallows in centralpart.Big Laminaria digitata and L. saccharina on stonesand shells of Modiola on the mud at 18-17 m, withDelesseria sanguinea (very big), Desmarestia aculeata,Brongniartella, Polysiphonia elongata, P. urceolata,Antithamnion plumula and A. boreale (very big). Southof Isle of Ven ("Sunbeam" station 82/63).Acta Phytogeogr. Suec. 50BALTIC PROPER, Swedish sideKRoK 1869; SJoSTEDT 1920 (Skane); LEVRING 1940(Blekinge, archipelago); Du RIETZ 1925a, 1930c and d,1932 b (Island of .J ungfrun in northern Kalmarsund,Stora Karlso near Gotland, Stockholm Archipelago);SVEDELIUS 1901 (Tjust Archipelago in Smaland, andGotland); the author's dredgings partly publ. in W JERN1950, 1952; in 1963 and 1964 with "Sunbeam"; KOLDE­RUP RosENVINGE's floras, with valuable informationon depths for algae in the Bornholm Sea.( l) Fucus vesiculosus belt with Pylaiella rupincola,Cladophora rupestris and H ildenbrandia pr·ototypus,mostly in shade of the Fucus, as also Phyllophoramembranifolia (LEVRING), Polysiphonia nigrescens,Furcellaria, species of Sphacelaria, etc. On betterlighted surfaces Ceramium tenuicorne, Dictyosiphonfoeniculaceus and Lithoderma subextensum.Lower border at ea. 10 m, sometimes less, 5 m(SJOSTEDT), 6-8 m (LEVRING). At Stora Karlso (Gotland)a dense growth of Fucus vesiculosus still at 10 m("Sunbeam" ). In very exposed positions in Blekinge(LEVRING) F. serratus occurs already at ! m togetherwith F. vesiculosus, otherwise at 3-5 m within thispart of the Baltic; F. vesiculosus and F. serratus occurhere down to 15 m.( 2 a) Fucus serratus beltonly far out at sea with aclean colourful tuft vegetationof Rhodomelaceae,Sphacelaria arctica, Aglaothamnionroseum, andthe crust Lithoderma Rosenvingii.Prevented fromreaching inshore by thebottom configuration orby the masses of smallsizedMytilus edulis developedin several areas.(2b) Inside of submarineshallows or islands occursa stout growth, heavyfrom Mytilus, of Furcellariawith Phyllophora,Ceramium spp., Ectocarpusconfervoides and Pylaiella.It turns at greaterdepth into a "warped"type with loose-and-entangledPhyllophora.Northernmost finds of F. serratus: Byerumsgrund NEof .Jungfrun , 14-15 m (Du RIETZ); Gotland, S half(KROK, SVEDELIUS).(3) Sphacelaria arctica-Lithoderma Rosenvingii belt.Deep-water vegetation (see WJERN 1952). In the southernBaltic at Davids Banke, between Bornholm andSkane, still with scattered Fucus serratus at 22 m andwith Laminaria saccharina at 22 and 24 m (theauthor). L. saccharina found between ea 20-30 m inthis area (see S0REN LUND 1947).(4) Dredgings by R. SERNANDER and Du RIETZ nearStora Karlso at 30-40 m (Du RIETZ 1925a): smallstones with Lithoderma . Similar vegetation also atJungfrun.