341 — 



whereas G. cylindraceum Fosl. is most closely related witli C. pusillum 

 (Lyngb.). 



E. Icel. KolfreyjustaOur. 



Codioluin pusiUiim (Lyngb.) Kjellm., Borgesen, Fser. Alg. p. 518; 

 Vaucheria pusilla Lyngb. Hydr. Dan. p, 72, tab. 22. 



The original specimens gathered by Lyngbye in the Faeroes and 

 described in Hydr. Dan. attain the same length as C!. gregarium. The 

 head is usually of the same length as the stalk, but specimens having 

 the head shorter or longer than the stalk also occur (cfr. also Borgesen 

 (I.e.) as shown by the following measurements: 



The head is nearly cylindric or indistinctly clavate, and merges 

 insensibly into the stalk. The head contains one reticular chromatophore 

 of a sack-like shape, with a longitudinal opening, containing numerous 

 pyrenoids without order. The membrane, measured in the upper part of 

 the head, has a thickness of 3 — 6 fx and consists of three layers as in 

 C. gregarium, and both the stalk and the membrane of the head consist 

 of a pectose as in C. gregarium. As far as I can see in the dried 

 material, the head contains a single nucleus, I have in Lyngbye's material 

 only met with sterile specimens. As may be seen from this description, 

 C. pusillum (Lyngb.) highly resembles G. gregarium A.Br.; the only dif- 

 ference between them is that G. pusillum for the most part has a nearly 

 cylindric head and G. gregarium for the most part a distinctly clavate 

 head. Judging from the description and figures of G. cylindraceum given 

 by Foslie ^) and original specimens here at the Botanical Museum, it is, 

 as I have said before, most closely related with G. pusillum, but still in 

 some respects it resembles G. gregarium and seems thus to have an 

 intermediate position. As G. cylindraceum Fosl. yet is unsufficiently known, 

 especially regarding shape and structure of the chromatophore, number 

 of nuclei and the substance of the membrane, it is not justifiable, at 

 present, to unite G. pusillum and G. gregarium, on account of its inter- 

 mediate position. 



') Foslie: Arct havalg. i). hi, PI. II, fig. 1 ; Nye havalg. p. 189. 



