734 



cannot produce receptacles in this unfavourable habitat. The Hi- 

 777a/?//2a//a- association is so diaracteristic on exposed coasts, that 

 a luxuriant growth of this alga is a sure sign of the presence of 

 surf. It is an association particularly fitted for resisting the dashing 

 of the waves; the surf constantly washes over the association at 

 low tide, and the metre-long, pliable, elastic receptacles of the 

 Himanthalia follow resistlessly the movement of the sea. Himaii- 

 thalia cannot stand to be dry for any length of time; when found 



Fig. 155. The Him.anthalia-assoc\a.i\on. Besides plants with receptacles, young plants are seen. The sub- 

 vegetation consists of Gigartina mamillosa, Polysiplionia urceolata. Acrosiphonia, Corallina, etc. The illustra- 

 tion is taken from Midvaag. (F. B. phot.) 



on a sheltered coast, where however it is rare, it always grows 

 sublittorally in low w^ater and often has another appearance. The 

 receptacles are uneven, sometimes inflated, and the colour of the 

 plant becomes a lighter yellowish-brown. 



As a subvegetation to the //zma/^^/irt/zo- association, Gigartina 

 mamillosa, Acrosiphonia, Polysiphonia urceolata, and others often oc- 

 cur besides Corallina (see fig. 155). Elachista scutulata has occa- 

 sionally been found growing on the receptacles, and on the old plants 

 a great many epiphytes are sheltered, especially species of Ectocarpus 

 e. g. E. fasciculatus, E. Hincksice, E. tomentosus and E. litoralis, species 



