— 146 - 



Rhodochorton Rothii (Turt.) Naeg., Rosenv., Grl. Havalg. p. 791. 



It is very abundant and gregarious on stones in the litoral region 

 and forms an undervegetation in the Fucus- zone. It occurs also in the 

 sublitoral region on the stems of Laminaria hyperborea to a depth of 

 c. 10 fathoms. 



The litoral specimens collected in March— October are always sterile 

 with exception of few specimina collected in July at Grjötnes in N. Icel. 

 The sublitoral specimens collected in the summer, in July, at Vattarnes 

 in E. Icel., in a depth of 10 fathoms, growing between the fibers of La- 

 minaria hyperborea, are with tetraspores. The specimens growing on the 

 old stems of Lam. hyperborea collected in the spring, in March— April, 

 at Reykjavik, are also with tetraspores. 



In the literature I have only seen fructiferous summer-specimens of 

 R. Rothii mentioned by Kjellman *) , collected by him at Spitzbergen 

 in July. 



The litoral, sterile specimens are usually c. 5 mm. high and the 

 fructiferous specimens collected at Grjötnes 13 mm. high. The thickness 

 of the filaments are 10 — 18/j, and the cells are 1—5 times longer than 

 broad. 



At Vestmannaeyjar it formed on very exposed rocks in the litoral 

 zone almost globular, solid tufts, with the basal filaments densely inter- 

 twisted, the f. globosa Kjellm. (The Algæ of the Arctic Sea). Lyngbye 2 ) 

 mentions similar forms of the R. Rothii and utters thereabout: „interdum 

 ad latera rupium glomerulos durissimos formantes". 



The branches of the specimens collected at Grjötnes have, instead of 

 one, one to three bunches of fructiferous branchlets. Either the branches 

 have one or a few bunches in different heighth, or the branchlets after 

 the extrusion of the spores grow long and bear one to three bunches of 

 fructiferous branchlets 3 ). These specimens are considerably higher than 

 the common, sterile Icelandic specimens, and resemble somewhat the 

 B. intermedium Kjellm. (Spetsbergens Thallophyter p. 28 (1. c.)) , but as 

 they generally very well agree with R. Rothii, I refer them to it without 

 hesitation. The R. intermedium is very closely related to R. Rothii and 

 is probably not specifically distinct from it, differing only by the heighth 

 of the vertical filaments (2 — 3 cm.); all the other characters mentioned 

 hi Kjellman's description of R. intermedium (1. c.) agree as well with 

 R. Rothii as with R. intermedium. 



1 ) F. R. Kjell m an: Om Spetsbergens marina, klorofyllförande Thallophyter, 

 Bihang till K. svenska Vet. Akad. Handlingar. Band 3. Stockholm 1875. 



2 ) H. B. Lyngbye: Tentamen Hydrophytologiæ Daniæ. Hafniæ 1819, p. 129. 



3 ) Somewhat similar specimens are mentioned by K. Rosen vinge in Grl. Hav- 

 alger (1. c). 



