226 BRITISH SEA-WEEDS. 



branched ; branches robust, either simple or divided, alter- 

 nate, densely clothed with shaggy, coarse, irregularly divided 

 branchlets, those of the upper divisions of the frond com- 

 paratively long and slender. All the branches are crowded 

 with narrow pinnate plumules, furnished with spreading 

 acute pinnules. Favellse in pairs on the pinnules of the 

 plumules ; tetraspores tripartite, minute, stalkless, on the 

 inner sides of short processes which issue from the pinnules 

 of the plumules. 



"Were it not for a difference in the colour, this species 

 might be more readily mistaken for Sphacelaria scoparia 

 than for any species of Callithamnion, and it is difficult 

 to believe that there is any affinity between its coarse 

 shaggy fronds, and those of its more delicate allies. It 

 is common, and grows on the perpendicular sides of 

 rocks left bare by the receding tide, from which it hangs 

 in long taper tufts of a dull red colour. 



Callithamnion Hookeri. Hooker's Callithamnion. 



Fronds growing singly or several together, from one to 

 four inches long ; stem indistinctly jointed, veined ; branches 

 alternate, spreading, flexuous, set with a second and third 

 series of branchlets, which are naked below and clothed with 

 nearly horizontal spreading plumules above ; the joints 

 throughout the plant are twice as long as broad. Pavellae in 

 pairs, without stalks on the plumules ; tetraspores spherical, 

 numerous, on the joints of the inner edge of the pinnae of 

 the plumules. 



This species is named after the late Sir William Jack- 

 son Hooker, of Kew. It is pretty generally distributed all 

 round our coasts from north to south ; it grows parasiti- 



