Ceramium-Studies. 



I and II. 



By 



Henning E. Petersen. 



With plates I — V. 



I. Remarks on Danish species of Ceramium. 



With plate I. 



In this little paper I shall make some remarks on certain 

 Danish species of Ceramium, viz.: C. tenuissimum, strictum, Are- 

 schougii, fruticulosum and rubrum. 



As to C. strictum, diaphanum and fruticulosum questions of 

 systematical nature will especially be discussed here. As well- 

 known it is very difficult to limit the two first named against each- 

 other, because they are very variable and as their authors have 

 not given reliable descriptions of them. In a previous paper (1908) 

 I have mentioned both C. diaphanum and C. strictum. The first 

 species is undoubtedly rightly concerned; the latter is perhaps not 

 the genuine form of C. strictum but, as I suppose, a particular 

 Danish or Baltic form, at all events a distinct species, different 

 from C. diaphanum; until another view may be proposed, I refer 

 it to C. strictum. 



The name "C. fruticulosum" has lately been rejected by H. 

 Kylin (1910). An examination of the original specimens of Kiitzing, 

 placed at my disposal by Mrs. Weber-van Bosse, for which kind- 

 ness I am much obliged, proves, that this name undoubtedly is 

 connected in right manner to the species in question. 



Further I shall give some informations on the réfringent bark- 

 cells containing proteid-matter which are common in some species, 

 and on the development of main axes in C. rubrum, fruticulosum 

 and diaphanum. 



Ceram. tenuissimum (Lyngb.) Ag. 



In a living specimen, dredged near Hirsholmene, I observed 

 that the contents of the chlorophyl-less refracting bark-cells were 

 formed into a crystalloid. As on this occasion I was hindered in 



Botanisk Tidsskrift. 31. Bind. 7 



