708 



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

 cepted in the sense applied by him to Ihis word, it, however, mainly 

 coincides \vith the term »formation«. 



The species which form these formations and associations, 

 often (litTer widely from each other in outer habit, their growth- 

 form may vary mnch; but ecologically they must of course as a rule 

 demand the same physical conditions (Hght, the temperature of 

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

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

 do not grow under the same conditions as the smaller epiphytes 

 which hnd their home on them. Epiphyles growing under the 

 thailus of larger algæ are exposed to a w^eaker light, and on the 

 beach larger algæ not only shade smaller epiphytes by 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 algæ, 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 Rosen vinge in his report on the 

 algæ-flora of the coast of Greenland (71, p. 189), that Kjell man '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 satisfaclory, and in so far as the Færoes are concerned, 

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

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

 Færoe Isles really extends far beyond, in more exposed piaces 

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

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

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

 most limit of the algæ-vegetation. According to Rosen vinge, the 

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

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

 sheltered piaces in the Færoes. It is true, that sheltered piaces 

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



^ Lorenz, I. R., Phj'sicalische Verhaltiiisse und Vertheilung der Organismen 

 im Quarnerischen Golfe. Wien 1863. Page 188 lie defines tlie facies as follows: 

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

 (Typen) derselben, betrachtet vom Standpunkte der Location und der bed i ugen- 

 den physicalischen Agentien.i: 



