819 



he has met wilh Rhodomela siibfnsca, Ceramium dinphaniim, Sphnce- 

 larin cirrhosa and other algæ floating al)out in the sea. 



But even if the algæ cannot of themselves float about in the sea 

 for a long time, they can nevertheless be carried about by adhering 

 to floating timber or other objects tloating on the surface of the sea. 



Between Shelland and the Færoes I have several times seen 

 floating timber complelely covered by a dense vegetation of algæ. 

 In Nolsofjord near Thorshavn, I once saw a large beam quite 

 overgrown by algæ. Amongst these were a great many well-de- 

 veloped Alnria esculenta, carrying numerous Litosiphon Laminariæ 

 on their lamina, several species of Ectocarpus , small forms of En- 

 leronwrpha. Diatoms, etc. Another time I found a piece of cork with 

 a dense, velvet-like vegetation, consisting oi Callithamnion scopiiloriim. 

 Finally, algæ destitute of air-bladders can be carried a long distance 

 by the sea-currents, eilher by growing on species provided with 

 bladders or only entangled among such algæ. 



To the factors contributing to the distribution of the algæ one 

 must be added which is certainly of no small importance now- 

 adays, that is: man's agency. There can hardly be any doubt, that a 

 great many species of algæ are carried far by the aid of navigation. 

 It is a well-know^n faet that ships which lie near to land very 

 quickly become green below the water-line. The reason is, that 

 the part of the ship which is under the surface of the sea is cov- 

 ered after a short time by a great many animals and piants, which 

 thrive excellently on account of the movement of the ship, and the 

 ensuing constant renewal of water. On a ship one can meet with 

 a vigorous algæ-vegetation, rich in different species^. 



^ The foUowing species were for instance collected by me on the 13th of June 

 1900 from the »Guldborgsund«, which had been scraped and scrubbed on the 

 15th of May of the same year, according to the journal of the ship. The species 

 were: large, vigorous Alaria esculenta, several specimens more than one foot long; 

 they preferred the most »exposed« parts of the ship, some specimens for instance 

 grow on the screw, where however the lamina were somewhat torn and split. 

 Of Laminaria. there were Laminaria saccharina and L. digitata, ca. half a foot 

 long. Further fairly large specimens of Porphyra miniata, smaller specimens of 

 Chordaria flagelliformis. Of green algæ there were Monostroma fusciim , small 

 Enleromorpha and a great many quite small specimens of different species, Diatoms, 

 etc. which I did not get an opportunity of examining. This comparatively luxuriant 

 vegetation had thus been produced during about one month. It must of course 

 not be left out of consideration, that if the bottom of a ship is ever so thoroughly 

 cleaned, it will never become perfectly clean, unless it is taken into dock. In the 

 above mentioned case, however, one may take it for granted, that only small spe- 

 cimens or fragments of algæ had been left. As to the transport of algæ by ships 

 see also Kjell man (48, pag. 59). 



