232 BRITISH SEA-WEEDS. 



upper plumulate ; plumules slender, distantly once or twice 

 pinnate; pinnae alternate, or on one side only, slightly 

 tapering, often branched at the tip; articulations of the 

 branches six or eight times as long as broad, of the branch- 

 lets three to six times. Eavella? in pairs, generally ter- 

 minating truncated branches ; tetraspores tripartite, large, 

 stalkless, on the pinnules of the plumules. 



The substance of this species is very gelatinous and 

 tender, and the natural colour of perfect specimens a 

 brilliant pink. It grows on Algse in tidepools, especially 

 on Codium tomentosum. It is annual, and of frequent 

 occurrence. In external appearance it resembles C. co- 

 rymbosum, but its mode of branching, and other cha- 

 racters, are sufficiently distinct when examined under a 

 microscope. 



Callithamnion interruption. The interrupted 

 Callithamnion. 



Fronds growing parasitically on Algss, much branched ; 

 branches alternate, somewhat lanceolate. Tetraspores cru- 

 ciate, on short stalks, on the inner side of the axils of the 

 branches. 



This species is figured in the ' English Botany } as 

 Conferva interrupt a, and is retained by Professor 

 Agardh in his ' Species Algarum/ but is omitted from 

 the ' Phycologia Britanuica/ I do not possess a spe- 

 cimen, nor have I been able to borrow one. Never- 

 theless, I do not like to omit a plant that has been re- 

 corded as British, and whose identity with any other 

 species I cannot satisfactorily establish. 



Callithamnion roseum. The rosy Callithamnion. 



Fronds growing in dense tufts, three or four inches long ; 



