821 



had been cultivaled for a long time. And in a paper (Verhalten 

 einiger mariner Algen bei Ånderung des Salzgehaltes. Oesterr. bol. 

 Zeitschrift, 1904) Karl Techet in his »Ubersicht« comes to Ihe 

 follow'ing conclusion: »Die individuelle Anpassungsfåhigkeit — um 

 diese handelte es sich bei den angefiihrten Versuchen — an An- 

 derungen des Salzgehaltes ist bei marinen Algen eine ziemlich weit- 

 gehende und zwar sowohl bei spontaner Erhohung als sponlaner 

 Verminderung der Salzintensitåt.« 



With regard lo change of salinily, I may also call attention to 

 Ihe difTerent o])servations mentioned in my descrij)lion of Ihe 

 vegetation. I have met with algæ, even Florideæ, growing al Ihe 

 mouths of rivers, where Ihey were completely covered by fresh 

 water at Iow tide, and by salt water at high tide^ These are 

 sudden changes. 



With regard to the temperature, the algæ seem specifically until 

 for resisting changes from cold to warm waler. They can prob- 

 ably stand the reverse change much belter, within certain limits 

 of course^. 



Algæ carried about by a ship are naturally much more exposed 

 to the danger of sudden changes in the temperature and salinily, 

 and if such changes occur the algæ simply perish^. But for short 

 distances, as for instance belween the Shelland Isles and the Fær- 

 oes, the difference is too small lo hurt the algæ. 



It is very probable, thai the white light on the surface may 

 hurt some of the algæ, which usually grow deepest down, when 

 they happen to be carried near the surface of the sea, but \ve know 

 nothing for certain. We may however suppose, that they are some- 

 times prolecled against Ihe white light; for instance by growing on 

 the under side of wrecks or by being enlangled belween larger algæ. 

 The motion of Ihe waves also perhaps serves to protect them in 

 some way, as it constantly makes them lurn anolher side to Ihe 

 light. We may also suppose that sublitloral algæ which have be- 

 come altached as spores lo floaling timber, elc. are perhaps belter 



^ See also Gomoiit, Sur la vegetation de quelques sources d'eau douce 

 sousmarines. (Bull. soc. hot. Fr., t. 51, 1904). 



^ Cf. Kjellman, Norra Ishafvets Algflora, p. 73. 



^ I may brieth' illustrate this by an example. In the summer of 1899. the 

 »Guldborgsund« was more than usuallj' foul, and was therefore ordered to go in 

 dock at Copenhagen. But when it arrived there, the bottom of the ship was per- 

 fectly clean, all the algæ had perished and dropped from the ship, as soon as it 

 had entered the warm and less salt water of the »Sound«. 



