824 



there abundantly, if a postglacial land-bridge had existed, by aid of 

 which it might easily have made the passage. 



Several sublittoral algæ e. g. Chætopteris plumosa, Phyllophora 

 rubens, Dilsea ediilis, Brongniartella byssoides, etc. are also wanting 

 al the Færoes, though they are more or less frequent in the sur- 

 rounding seas. 



Wlien everything is taken into account, the algæ-flora from the 

 deeper sea has perhaps had the grealest difficulty in reaching the 

 Islands. This perhaps explains, why some sublittoral algæ which 

 might reasonably be expected to grow at the Færoes are not found 

 there. The sublittoral algæ which grow deep down are probably 

 the least fitted for floating a long time, and as to their adhering 

 to algæ from the littoral region or to floating timber as a means 

 of transport, this likewise seems to occur only rarely. On the other 

 band we know but little about the first stages of development of 

 many of these algæ. We especially want to know whelher the 

 difTerent reproductive organs are able to Hoat for a long time in 

 the sea apart from the mother-plant. They may possibly be carried 

 far about as plankton ^ Finally if the algæ spores cannot float 

 far either by themselves or by the agency of the sea currents, it 

 is hov^'ever probable, that they can stick to the mucilage of larger 

 algæ, or to tlie mucus of fishes, and thus be carried off. 



It is hardly probable, that any of the sublittoral algæ have 

 been able to survive the glacial period, according to Geikie^. He 



^ In connection with this it may be pointed out, that the late Prof. Cleve, the 

 well-known Swedish plankton-investigator, thinks it probable that algæ-spores can 

 be carried about bj^ tlie agencj^ of marine currents. He has even expressed the opi- 

 nion , that the stunted forms of algæ from the Polar Sea met with in the Baltic 

 can have been carried there together with Arctic plankton (see Botaniska Notiser, 

 1898, p. 269). If it is so, the short distance from the English coast to the Færoes 

 is nothing by comparison. It should however be observed that these forms of 

 algæ in the Baltic must rather be considered as »relicts« as pointed out by Sve- 

 deli us (Studier ofver Ostersjons Hafsalgtlora, p. 68— 69). 



A remark by Oltmanns should also be mentioned here. In a paper »Notizen 

 uber die Cultur- und Lebensbedingungen der Meeresalgen" (Flora 1895), after having 

 emphasized the necessity or at least the desirability of having sterilised sea water 

 for culture-experiments, he writes : »Die Steriliserung ist aber auch besonders dann 

 unerlåssig, wenn man kleine Ectocarpeen einigermas.sen rein cultiviren will, weil 

 das See w asser fast zu jeder Jahreszeit und an jedem Ort eine recht 

 e r h e b 1 i c h e A n z a h 1 von S c h vv ii r m s p o r e n der v e r s c h i e d e n s t e n Species 

 enthålt, welche alle neben den ausgesiiten Formen keimen wiirden.« 

 (The emphasis is mine.) 



^ Geikie, .lames, Prchistoric Europe. A Gcological Sketch. London 1881, 

 p. 663. 



