712 



are almost ahvaj^s covered by brown, red, and black crusts, re- 

 spectively consisting of Ralfsia, Hildenbrandia and Lichens. 



These algæ, with the exception o^ Ralfsia, must necessarily be able 

 not only to live for a long time witbout sea water and consequently 

 to be dried up, but also to be wasbed by fresh water. They are 

 moreover excellently fitted for resisting the surf, as they are very 

 firmly attached to the rocks, of which they may ahnost be said to 

 form a part. Lastly, they must be well fitted to stand intense light 

 and great changes of temperature, as the southern side of rocks is 

 often much heated by the sun. 



On the west coast of Sydero at Vaag's Ejde 1 have seen extensive 

 growths of Ralfsia, which are here found in large flat littoral pools 

 with only a few inches of water. Whilst Ralfsia thrives hest in 

 littoral pools with shallow water, Hildenbrandia wdll thrive excel- 

 lently in the latter, as w^ell as on steep rocks which are dry in 

 calm weather. 



Among other algæ contributing to form this formation, Pilinia 

 maritima, Pleurococcns spec, Codiolum gregarium, etc, which I have 

 found intermingled with crusts of bluish-green algæ, ought likewise 

 to be mentioned. 



This formation is exposed to clear daylight and to the varying 

 influence of the weather in its elevated habitats; in more low-lying 

 regions it will often be found as a subvegetation covered by different 

 larger algæ of the place. 



Almost in the middle of the beach or somewhat farther down, 

 this formation is replaced partly by Corallina officinalis, partly by 

 Phymatolithon polymorphiim, both spreading widely downwards into 

 the sublittoral region. 



Simmons briefly describes a »Hildenbrandtia-formaiion«, but 

 he says that it is only to be found »An ruhigeren Oertlichkeiten«, 

 and that »die Steine und Pelsen in der Wasserflache von dieser 

 Formation bedeckt sind.« Later on he gives (66, p. 173) a further 

 explanation of this formation, defining it as purely littoral. 



The Chlorophyceæ-Formation . 



The characteristic algæ of this formation are: Prasiola crispa 

 subspec. marina, different forms oi ,Enteromorpha intestinalis, Rhizo- 

 cloninm riparium, Prasiola stipitata, Prasiola furfiiracea and a few 

 other species. 



This formation stretches like a green belt along the exposed 



