— 342 



I have I'eferred to this species some plants, 1 met with in NW. Ice- 

 land growing at high-water mark in company with Ulothrix consociata and 

 Urospora mirabilis. My plants attain a length of about 1 mm., the head 

 is usually shorter than the stipe, sometimes longer or sometimes of about 

 the same length as the stipe as shown by the following measurements. 



The head is usually nearly cylindric and merges also usually insen- 

 sibly into the stalk, but still I have seen some few plants having the 



head indistinctly separated from the stalk by 

 a constriction. The chromatophore is of the 

 same shape and structure as in G. gregarium 

 and contains numerous pyrenoids. The thick- 

 • ness of the membrane, measured in the upper 

 part of the head, is 3 ^/, and both the stalk 

 and the membrane of the head are of the 

 same structure as in G. gregarium and consist 

 also of pectose. Among my material, which 

 was gathered in the beginning of September, 

 I found some fructiferous specimens. The 

 spores are ovate or oblong-ovate and are 

 furnished with a tail resembling that of the 

 spores of Urospora, they have, as far as I 

 can see in my alcohol material, two cilia in the broader end, and are 

 4— 6 /i broad and 14 n long. 



NW. Icel. Kolbeinsa. 



Fam. Ulvacese. 



Perciirsai'ia perciirsa (Ag.) K. Rosenv. Grl. Havalg. p. 903. 



I have met with this species growing in company with Rhizoclonium 

 in pools at or a little above high-water mark. Fructiferous specimens 

 have been gathered in July. The frond of my specimens consists for the 

 most part of two rows of cells, but I have not seldom met with plants, 

 which were partly composed of one cellrow. The filaments are 26 ji 

 broad and about 14 ft thick. The cells are usually rectangular, somewhat 



Fig. 3. Codiolum pusillum 

 (Lyngb.). To the left the 

 lower end of the head con- 

 taining spores; to the right 

 two spores (compare the text). 

 (550:1.) 



