488 



up on the hills at a height of some 600 feet 1 ; it occurs in piaces 

 where it is liable to be left dry for a long period and in others 

 where it is never left uncovered. It grows sometimes in dimly 

 lighted clefts in the rock and in caves, sometimes in piaces ex- 

 posed to the full rays of the sun. Sometimes it is found altached, 

 sometimes it occurs in detached, floating examples. As these dille- 

 rent conditions must exercise a very marked inlluencc both on its 

 outer habit and its anatomicai structure it seems well-nigh hopeless 

 to arrive at any definite conclusion as to the variations in the 

 different »species«, until we have by means of experimental culturc 

 come to an understanding with regard to the species themselves, 

 the greater part of which according to my opinion are nothing 

 more than biological forms. As already mentioned, the most con- 

 llicting theories have been propounded in books as to the defini- 

 tion of this species, of which I will merely mention some of the 

 most important, from modern writings. It is especially the Swedish 

 algologists who maintain that the genus ought to be divided into 

 a great many species, as does also Ahlner in his monograph of 

 the Swedish Entomorpha-spec'ies, where he lavs particular stress on 

 the anatomicai characters as marks of distinction. Kjell man and 

 Agardh express much the same opinion on this question, though 

 the latter differs in several points from Ahlner. Quite another 

 definition of species is represented by Le Jolis, who, in his work 

 »Liste des Algues marines de Cherbourg,« records, on the one hånd, 

 only a few species, but, on the other, a great many" varieties and 

 forms; he lays especial stress on the outer form. In »Grønlands 

 Havalger« Rosenvinge follows the opinion of Le Jolis, but with 

 some modifications; thus, e. g., he makes use more particularly of 

 the anatomicai structure as a basis; but in spite of the somewhat 

 scanty material from Greenland which he had at his disposal, he 

 emphasizes the faet that it is impossible to separate the species. 

 Lastly, I must mention Re in bo Id 's »Die Chlorophyeeen der Kieler 

 Fohrde« which has been of great use to me in working up the 

 Færoese material. Reinbold follows more particularly J. Agar dh' s 

 view mentioned above, and, consequently, enumerates many species, 

 though he makes it clear in his description how diflieult it is to 

 keep Ihem distinct. 



The following description is based on an examinalion of much 



1 Borgesen, F.: Freshwater Algæ (Botany of the Færoes, Part I. p. 243). 



