714 



of the waves. Prasiola crispa '■'marina and Rhizoclonium may like- 

 wise be protected by the great llexibility and elasticity of their 

 Ihallus. The upper limit of this algæ-vegetation changes as the 

 locaHty becomes more or less exposed, the lower limit likewise 

 gradually moving downward as the locality becomes more sheltered. 

 Several of these algæ, for instance, Prasiola stipitata and Entero- 

 niorpha, may be found rather far down in the littoral region, in 

 more sheltered piaces. 



This green algæ- formation may be divided into several asso- 

 ciations according to the predominant characteristic algæ. Naming 

 them from the top downward: a Prasiola crzs/?a-association, a Rhi- 

 zoc/o77f«/7i-association, an Enteromorpha intestinalis-associai'ion and a 

 Prasiola stipil ata-assoc'iaiion. 



The Prasiola cnspa- association is found at least 40 feet above 

 the level of the sea^ It prefers steep, precipitous rocks, on which 

 it is found as a dense cover, turning light yellowish-green when 

 it dries up. This light colour makes it stand out against the dark 

 rocks to which the thallus is fixed. When moist it turns dark 

 green, each thread becomes free and sways with the waves. As 

 subvegetation we find blackish lichen crusts, which have been de- 

 fined by the Rev. Deichmann Branth as Verrucaria mergacea, 

 V. maiira, V. mucosa and V. striatula. 



The i?/izroc/o/7»i777- association may be found at the same level 

 above the sea, but it prefers moist localities, for instance, such 

 where fresh water is constantly dripping down, or pools and caves, 

 where the air is very damp. I never found this alga perfectly dry; 

 it is evident that it cannot stand to be dried up. It often forms large, 

 unmixed growths and is easily discernible on account of its light- 

 green colour and its often crisp, almost curly, appearance. In some 

 piaces, at Glivernæs for instance, I have found Vaucheria coronata 

 at about the same level in moist, but more sheltered little depres- 

 sions in the rock. 



The £'77/e/-on7orjD/7«-association is generally found farther down, 

 but on an exposed coast it may reach to about the same height, 

 that is ca. 40 feet. It consists for the most part of Enteromorpha 

 intestinalis var. micrococca , and smaller forms of var. gennina, 

 especially f. cornucopiæ. Enteromorpha prefers piaces where fresh 

 water oozes from the rocks, but also grows in dry piaces and 



^ As before mentioned, several of these algæ, ho^\evcr, may l)c found growing 

 scattered at least twice as high up on the rocks. 



