732 



Mingled with the characteristic algæ, we find e. g. Ceramiiim ru- 

 briini, Cladophora riipestris, and very rarely Cladostephiis spongiosus. 

 Corallina is usually absent in this association, as the dense growtli 

 of both species leaves no room for a subvegetation. 



This association, \vhich is very common in the Færoes, has 

 not been described by Si m mon s, nor by any Norwegian investi- 

 galor. It is however undoubtedly closely connected with Han- 

 steen's »Broget-pclagiske-formation« (38, p. 348) and partly related 

 to Boye's »Gigartinaformation« (6, p. 22 — 23). 



The Gigartina- Association. 



Somewhat above the lowest water mark, the height varying ac- 

 cording to the exposure of the locahty, a vegetation of Gigartina ma- 

 niillosa (see plate XVIII and XXI), often dense and up to 6 inches high, 

 is found in the Com//ma-formation. This association often extends 

 far horizontally, and on almost horizontal rocks, found within the 

 level of this association, it is often widely distributed (see plate XVIII). 

 Vertically it usually reaches only to a height of one or two feet; 

 the height being the greatest on specially exposed coasts. 



Epiphytes common on Gigartina are: Chantransia virgatnla, very 

 often forming a dense, velvety covering on the stalky part of the 

 thailus, and Dermatolithon macrocarpum f, færoensis which grows 

 on it in smaller or larger pale pink incrustations. Ceramium ru- 

 lyrnm, Chondrus crispus, Polysiphonia urceolata, Acrosiphonia alhe- 

 scens, and frequently some younger or older piants of Himanthalia 

 lorea, besides Corallina officinalis, are found mingled with Gigartina. 

 But generally these algæ are only few in numbers, or they may be 

 totally wanting, so that the dark reddish-brown colour of the Gigar- 

 tina predominates. Gigartina mamillosa grows luxuriantly in the 

 most exposed piaces. Its tough, cartilaginous character probably 

 makes it well fitted for resisting the surf. It is hardly exposed to 

 any drying process, as it generally grows at the Iower part of the 

 littoral region. 



According to Hansteen (38, p. 348), and Boye (6, p. 22), a si- 

 milar G/g'ar/ma-association is found along the west coast of Nor- 

 way. It seems to differ from the Færoese association only in its 

 colour. Boye writes: »It (the formation) is easily distinguishable 

 at a long distance as a light yellowish green belt, immediately above 

 the lowest water mark, because the algæ inviduals are faded by the 



