234< BRITISH SEA-WEEDS. 



and is annual. The long, slender, comparatively naked 

 branches, and the short, awl-shaped branchlets are cha- 

 racters which will readily reveal its identity to the col- 

 lector who may have the good fortune to discover it. 



Callithamnion plumula. The little feather Calli- 

 thamnion. 



Fronds growing in tufts, from two to six inches in length, 

 flaccid, distichously branched ; branches alternate or forked, 

 repeatedly divided; plumules once or twice pectinate on 

 their upper side, springing in pairs, or, in luxuriant spe- 

 cimens, in threes and fours, from near the apex of every 

 joint of the stem and branches, about half a line to a line 

 in length. Favella? in clusters, on the tips of the main 

 branches, which are always shortened ; tetraspores cruciate, 

 on the tips of the comb-like pinnules of the plumules. 



This is one of the most common, easily recognised, 

 and elegant species of this beautiful genus. The comb- 

 like plumules clothing every joint of the plant are so 

 visible to the naked eye, that a microscope is scarcely 

 necessary to determine its identity. Tt grows on rocks 

 and sea-weeds near low-water mark, and also in deep 

 water, whence it is often washed on shore. Specimens 

 differ occasionally in the luxuriance of the plumules ; 

 in some they are short and thick, in others long and 

 very delicate. The colour varies from carmine to light 

 brown ; the substance is soft and tender, and the plant 

 adheres closely to paper when dry. 



Callithamnion cruciatum. The crossed Calli- 

 thamnion. 



Fronds growing in tufts, one to two inches long, flaccid, 



