488 
np on the hills at a height of some 600 feet 1 ; it occurs in places 
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 places ex¬ 
posed to the full rays of the sun. Sometimes it is found attached, 
sometimes it occurs in detached, floating examples. As these diffe¬ 
rent conditions must exercise a very marked influence both on its 
outer habit and its anatomical 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 culture 
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¬ 
flicting 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- species, where he lays particular stress on 
the anatomical characters as marks of distinction. Kj ell 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 byLe Jolis, who, in his work 
»Liste des Algues marines de Cherbourg,« records, on the one hand, 
only a few species, but, on the other, a great many varieties and 
forms; he lays especial stress on the outer form. In »Gr 0 nlands 
Havalger« Rosenvinge follows the opinion of Le Jolis, but with 
some modifications; thus, e. g., he makes use more particularly of 
the anatomical structure as a basis; but in spite of the somewhat 
scanty material from Greenland which he had at his disposal, he 
emphasizes the fact that it is impossible to separate the species. 
Lastly, I must mention Reinbold’s »Die Chloropliyceen der Kieler 
Fohrde« which has been of great use to me in working up the 
Fseroese material. Reinbold follows more particularly J. Agardh’s 
view mentioned above, and, consequently, enumerates many species, 
though he makes it clear in his description how difficult it is to 
keep them distinct. 
The following description is based on an examination of much 
I 
1 Borgesen, F.: Freshwater Algae (Botany of the Faeroes, Part I, p.243). 
