821 



had been cullivaled for a long time. And in a paper (Verhallen 

 einiger mariner Algen bei Anderiing des Salzgehaltes. Oesterr. bot 

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

 following conclusion: »Die individuelle An])assiingsfahigkeit — 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 spontaner 

 Verminderung der Salzintensitat.« 



With regard to change of salinity, I may also call attention to 

 the different observations mentioned in my description of the 

 vegetation. I have met with algae, even Floridece, growing at the 

 mouths of rivers, where they were completely covered by fresh 

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

 sudden changes. 



With regard to the temperature, the algae seem specifically unfit 

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

 ably stand the reverse change much better, within certain limits 

 of course^. 



Algae carried about by a ship are naturally much more exposed 

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

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

 distances, as for instance between the Shetland Isles and the Faer- 

 oes, the difference is too small to hurt the algae. 



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

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

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

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

 times protected against the white light; for instance by growing on 

 the under side of wrecks or by being entangled between larger algae. 

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

 some way, as it constantly makes them turn another side to the 

 light. We may also suppose that sublittoral algae which have be- 

 come attached as spores to floating timber, etc. are perhaps belter 



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

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



^ Cf. Kj ell man, Norra Ishafvets Algflora, p. 73. 



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

 jGuldborgsund« was more than usualh' 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 algae had perished and dropped from the ship, as soon as it 

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



