Immigration of Algæ into Danish Waters

Abstract

THANKS to the careful studies of the late Prof. Rosenvinge on the vegetation of Algae in Danish waters, particularly in the ‘nineties, we are now able to study the changes since that time in the algal flora. An increase has occurred in this flora, amounting to five species during the past fifty years: the red alga, Trailliella intricata, Batters ; the two green algae, Codium dichotomum (Huds.) Setchell (= C. tomentosum (Huds.) Stackh.) and Codium fragile (Sur.) Hariot (= C. mucronatum J.Ag.) ; and the brown algae, Dictyota dichotoma (Huds.) Lamour. and Colpomenia peregrina Sauv. (= C. sinuosa var. peregrina Sauv.). The first three mentioned were recorded by Rosenvinge1, the last two by Lund2,3. They are forms of a somewhat more southern origin, which have gradually spread towards the north ; but the Danish localities are not their northernmost limits, for they were also met with on the west coast of Norway. They are all known from the coasts of Great Britain.