819 



he has met with Rhodomcla siihfusca, Ceraniiiim diaphanum, Sphace- 

 laria cirrhosa and other algae floating ahout in the sea. 



But even il" the algae cannot of themselves float ahout in the sea 

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

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



Between Shetland and the Faeroes I have several times seen 

 floating timber completely covered by a dense vegetation of algae. 

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

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

 veloped Alaria esciilenta, carrying numerous Litosiphon Laminarke 

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

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

 a dense, velvet-like vegetation, consisting o{ Callithamnion scopiiloriim. 

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

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

 bladders or only entangled among such algae. 



To the factors contributing to the distribution of the algae 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 algae are carried far by the aid of navigation. 

 It is a well-known fact 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 plants, 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 algae-vegetation, rich in different species ^ 



^ The following 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 esciilenta, 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 lamiiia were somewhat torn and split. 

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

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

 Chordaria flagelliformis. Of green algie there were Monostroma fiisciim, small 

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

 etc. which 1 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 alga^ had been left. As to the transport of algae by ships 

 see also Kj ell man (48, pag. 59). 



