- 147 — 



The specimens growing on the old stems of Laminaria hyperborea 

 resemble the R. Rothii in everything, except that the basal filaments are 

 creeping in the subepidermal tissue . of the Laminaria stems. At first I 

 thought that the plant was an endophyte, but by further examination of 

 the Laminaria tissue, I am convinced, that 

 it is only a pseudo-endophyte. The sur- 

 face of the Laminaria stems was rough, 

 the epidermal layer had fallen away, the 

 intercellular substance of the subepidermal 

 tissue was disorganized, and the cell-rows 

 in many cases split. The basal filaments 

 of the Rhodochorton were creeping in the 

 dead tissue, but the death of the tissue did 

 not seem to have been caused by it. 

 Sometimes it is difficult to see whether 

 the Rhodochorton has caused the destruc- 

 tion of the tissue, or not, but several 

 times it is easily seen, that the tissues 

 were dead when the Rhodochorton ap- 

 peared. The Polysiphonia urceolata, which 

 grew among the Rhodochorton on the 

 Laminaria stems in the dead tissue, was 

 a „pseudo-endophyte", in the same manner 

 as the R. Rothii. 



The R. pafetsiticum Batters l ) is cer- 

 tainly identical with the R. Rothii growing 

 in the dead tissue of the Laminaria stems. 



Fig. 3. Rhodochorton Rothii. 

 Transverse section of part of the 

 stem of Laminaria hyperborea 

 showing the Rhodochorton fila- 

 ments creeping in the dead and 

 dying tissues (138: 1). 



E. lcel. Vattarnes. 

 N.I c el. Grjötnes (CO.). 

 NW. Icel. Dyrafjöröur (CO.). 



S W. lcel. Probably common. Ölafsvik, Brimnes, Reykjavik, Hafnar- 

 fjöröur. 



S. Icel. Vestmannaeyjar. 



Rhodochorton repens H. Jonsson nov. sp. 



Planta epipbytica c. 1 mm. alta, fîlis erectis 8 — 13 /j. crassis e 

 basi a filis repentibus constitute) egredientibus, inferiore parte nudis, 

 superiore autem circiter a medio ramosis. Rami sparsi, alterni, 

 sæpe secundi (præsertim rami superiores), interdum oppositi, et in 

 supremo axi primario corymbosi, sporangia gerentes. Rami (rarnuli) 

 infimi et supremi breves, medii autem interdum elongati. Sporangia 



] ) E. A. Batters: New or critical British marine Algæ. Journal of Botany. 

 Vol. 34. London 1896 



