224 BRITISH SEA-WEEDS. 



Callithamnion spongiosum. The spongy Calli- 

 thamnion. 



Fronds from two to four inches long, flaccid, spongy ; 

 stem with indistinct joints, veined, much branched; 

 branches of two or three series, long, thickly clothed with 

 quadrifarious, round-topped plumules, which are furnished 

 with alternate, several times forked pinna?, with short, bifid, 

 very obtuse tips. Favellae large, generally in pairs, near the 

 tips of the plumules ; tetraspores tripartite, solitary, stalk- 

 less, in the axils of the pinna? of the plumules. 



Although, the colour of this species is never very bril- 

 liant^ and is easily deteriorated by exposure, the form 

 of the plant itself is so beautiful when perfect that it 

 always makes a handsome specimen. It must be laid 

 out immediately it is gathered, for it decays very rapidly. 

 It grows near low-water mark, either on rocks or sea- 

 weeds, is annual, and fruits in summer. 



Callithamnion Brodisei. Brodie's Callithamnion. 



Fronds growing in tufts about two inches high ; stem 

 slender, opake below, more or less jointed above, veined ; 

 branches alternate, spreading, veined, those below longest, 

 becoming gradually shorter upwards, the second or third 

 series furnished with alternate plumules; plumules pinnate, 

 with alternate, simple, spreading pinnules, from the iuner 

 side of the tips of which spring a few awl-shaped processes. 

 Favella? large, in pairs on the sides of the lesser branches, 

 which are frequently distorted; tetraspores oval, stalkless, 

 on the processes of the pinnules. 



This is peculiarly a British species, and has not been 

 found in any other country. It is parasitic, and grows 

 near low- water mark, is annual, and fruits in summer. 



