702 



rays which Ihey especially need, already become fainter at a 

 small depth. The red algae gfow deepest, as they need the green 

 rays, occurring at greater depths, the most; finally the brown 

 algae are specifically fitted for growing at a depth between that 

 of the green and the bluish-green algae on one side, and that of 

 the red algae on the other side. He calls our attention to the 

 fact, that the algae are very well able to accommodate themselves 

 to the colour of the light of their habitats. He refers to the 

 interesting observation made by Nads on, that certain Cyanophycece 

 and Chlorophycece are represented by green specimens, near the 

 surface of the sea, and by red, in deep water. This may also 

 happen on the coasts of the Faeroes, as I have already men- 

 tioned. Nadson thinks for instance, that Conchocelis rosea is a 

 deep water form of Ostreobium Oiiekettii. 



B e r t h o 1 d and 1 1 m a n n s determine the Floridecv as shade 

 plants, but this is criticised by Gaidukow, who asserts that Olt- 

 m a nil's experiment only confirms Engelmann's theory, that the 

 Floridece of deep water have the typical colour of the Floridece, be- 

 cause they grow in green and blue light, whereas they turn brown 

 and 3^ellow near the surface in the white light ^. 



The Engelm an n -Gaidukow theory on the w^iole coincides 

 with my observations ; still it seems to me that the quantity of the 

 white light must practically be of no small importance not only 

 to the colour of the algae, but also to their distribution. On the 

 coasts of the Faeroes, on the beach, and even above it, a great 

 many Floridece of a deep red colour are found, perhaps some- 

 times of a more reddish-brown, but I have hardly ever seen them 

 turning almost light yellow as the same species do, for instance, 

 on the west coasts of Norway or on our own coasts-. No doubt 

 this is due to the w^eaker light at the Faeroes, where fogs are fre- 

 quent, and the sky much overcast; and as a vegetation of Flo- 

 ridece, typically red and mcluding some of the forms usually 

 belonging to great depths, is often found in small inlets between 

 Thorshavn and Arge, in water not even 2 fathoms deep and 

 overshadowed by Laminarice, this is certainly also due to the 



^ 111 the West Indies Floridece growing in shallow water, exposed to direct 

 sunlight, are often perfectly- green, or hluish -green, e. g. Grateloiipa fiUcina. 

 Svedelius has observed the same fact on the shore of Cej^lon (compare: Bot. 

 Notiser. 1905, p. 181). 



- On one occasion I found Porphijra iimbilicalis turning yellow, in the 

 sounds north of Kvalvig. 



