394 



mentioned here and which are pointed out by Kjellman as the 

 chief marks of distinction between his Rh. intermedium and Rh. Rothii 

 cannot be regarded as denoting a distinct species, for I have found 

 all intermediate stages between the former species and typical Rh. 

 Rothii, which Jonsson 1 also claims to have done in the Icelandic 

 material. Perhaps it may be regarded as a special form of Rh. Rothii, 

 but at any rate the name intermedium is hardly correct, it being by 

 no means intermediate between the former species and Rh. ftori- 

 dulum — as Kjellman supposes — the latter being quite distinct 

 from Rh. Rothii, e. g. by its star-like chromatophores. 



Rh. Rothii occurs not only in the littoral zone but also in the 

 sublittoral on Laminaria hyperborea — as I quite agree with Jons- 

 son (1. c. p. 147) in thinking that the Rhodochorton , which is com- 

 monly met with on the stems of Laminaria hyperborea where it 

 occurs as a short, dense mat, is this species, and I am also of 

 opinion that Rh. parasiticum Batters 2 undoubtedly belongs to this 

 species as pointed out by Jonsson. Fig. 63 shows the basal 

 part, the erect filaments spring from prostrate ones creeping on La- 

 minaria hyperborea. How far this alga is really a parasite or only 

 a pseudo-endophyte as mentioned by Jonsson I shall not discuss 

 at any length, merely stating that where it occurs on the Laminaria 

 the tissue of the latter is always more or less destroyed, and there- 

 fore Jonsson is very possibly right when he savs that it can 

 only penetrate into the tissue, after the latter has been destroyed. 

 A single specimen which I found on a Lam inaria-s tipe which 

 Jonsson had gathered from Kalbakfjord differed in some points. 

 Fig. 64 shows some small portions of it. Besides the clustered tetra- 

 sporangia commonly occurring on Rhodochorton Rothii (see fig. 64 b) 

 it had also, as shown in fig. 64 a, solitary, terminal sporangia, 

 which were noteworthy by being much larger than the former, the 

 tetraspores in the clusters being 16/* broad, while the solitary ones 

 attained to a thickness of some 27 /*. The solitary sporangia were 

 borne on short, erect filaments, which were generally branchless; 

 the cells in these filaments were for the most part short, often only 

 just as long as broad, and frequently somewhat swollen in the 

 middle. On the other band, the filaments bearing the clustered 



1 Jonsson, H.: The marine Algæ of Iceland (I. Rhodophyceæ), Botanisk 

 Tidsskrift. 24. Bind, p. 14(5. 



2 Batters: New or critical British marine Algæ (Journal of Botany, vol. .'54, 

 189(5, p. 389). 



