708 



applied by Lorenz in his interesting and instructive paper ^ Ac- 

 cepted in the sense appHed by hfrn to this word, it, however, mainly 

 coincides with the term » formation «. 



The species which form these formations and associations, 

 often differ widel}^ from each other in outer habit, their growth- 

 form may vary much; but ecologically the}^ must of course as a rule 

 demand the same physical conditions (light, the temperature of 

 the air, the temperature and salinity of the sea, the dashing of 

 the waves, etc.). The large characteristic alga3 of the formations 

 do not grow under the same conditions as the smaller epiph^^tes 

 which find their home on them. Epiphytes growing under the 

 thallus of larger algae are exposed to a weaker light, and on the 

 beach larger algae not only shade smaller epiphytes b}' their thallus, 

 but also protect them from being dried or heated by the sun, from 

 the dashing of the waves etc. Protected by the larger algae, the smal- 

 ler, often more delicate species thus obtain suitable surroundings; 

 they are of course only found in localities answering to their re- 

 quirements. 



I. The Littoral Region. 



It has been pointed out by Rosenvinge in his report on the 

 algae-flora of the coast of Greenland (71, p. 189), that Kjellman's 

 determination of the limits of the littoral region as being re- 

 spectively the highest tide mark and the lowest ebb mark, is 

 not quite satisfactory, and in so far as the Faeroes are concerned, 

 Kjellman's determination is certainly not quite suitable. As to the 

 uppermost limit, the algae-vegetation on the exposed coasts of the 

 Faeroe Isles really extends far beyond, in more exposed places 

 most likely even more than 100 feet beyond , the highest water 

 mark. In sheltered places, subject to the influence of the tide, 

 the uppermost tide- mark will be almost identical with the upper- 

 most limit of the algae-vegetation. According to Rosenvinge, the 

 sea at springtide rises beyond the uppermost limit of the algae-vege- 

 tation in Greenland; this will hardly ever happen even in the most 

 sheltered places in the Faeroes. It is true, that sheltered places 

 with ebb and flood are but small in numbers here, so that my 



^ Lorenz, I. R., Physicalische Verhiiltnisse und Vertheilung der Organismen 

 im Quarnerischen Golfe. Wien 1863. Page 188 he defines the facies as follows: 

 »Die Facies sind also Vegetations- (oder Thier-) Formationen. oder Unterabtheilungen 

 (Typen) derselben, betrachtet vom Standpunkte der Location und der bedingen- 

 den pln^sicalischen Agentien.* 



