206 BRITISH SEA-WEEDS. 



len, coated with coloured cellules ; internodes transparent ; 

 those of the lower part of the stem many times as long as 

 broad, those of the minute branehlets very much shorter. 

 Spore-clusters in pairs, surrounded by long, forcipate, in- 

 volucral branehlets ; tetraspores projecting singly from the 

 nodes. 



In certain localities this species appears to be abun- 

 dant, as, for instance, near Kilkee, on the coast of Ire- 

 land, where Dr. Harvey first discovered it, in 1844, and 

 where it covered the rocks " almost to the exclusion of 

 every other species, both in places left bare at low water 

 and in the small tide-pools." Whether it be very local, 

 or whether it be frequently overlooked on account of its 

 small size, I do not know, but it is certainly considered 

 a rarity by ordinary collectors. It grows parasitically 

 on small algse, is annual, and matures in autumn. It is 

 so small, delicate, and gelatinous, that it is next to im- 

 possible to lay it out satisfactorily on paper. 



Ceramixun strictum. The straight Cer^miiun. 



Fronds growing in dense tufts, from two to four inches 

 high, very slender, and of nearly equal diameter through- 

 out, irregularly, forkedly branched, having narrow, acute 

 axils ; branches and branehlets erect and straight ; tips 

 forcipate, and slightly hooked; nodes somewhat swollen, 

 coated with minute, purple cellules, either quite smooth or 

 clothed with long, transparent fibres ; internodes three or 

 four times as long as broad, transparent. Spore-clusters in 

 the axils of the upper branches, embraced by a few short, 

 involucral branehlets ; tetraspores prominent, whorled round 

 the nodes in the upper divisions of the branches. 



The long, transparent fibres which clothe the nodes of 



