21 BTKOP8I8 OF BRITISH SEAWEEDS. 



analogous to that of the present genus. At a first glance 

 the difference in the structure of the frond between De* 

 marestia and Arthrocladia appears considerable, but a 

 closer examination removes much of the dissimilarity. A 

 jointed tube runs through the centre of both fronds; in 

 the Desmarestia, in the form of a slender filament ; in the 

 Arthrocladia of a wide tube. The confervoid filaments 

 ar • of the same nature in both genera, and the branching 

 of the fronds identical. The great difference lies in the 

 comparative density of structure. 



IX. SPOROCHNUS. 



21. pedunculatus (The pedunculated Sporochnus) ; stem undi- 

 vided ; branches lateral, Long, simple, horizontal; recepta- 

 cles elliptical, Ag. Sp. Alg. v. 1. p. 149. (Atlas, PL VI. 

 Fig. 21.) 



Gigartina pedunculata, Lam. Fucus pedunculatus, Huds. 

 Ilab. On submarine rocks, shells, etc., near low-water mark, and 

 at a greater depth ; rare. Annual. Summer and autumn. 

 Sporochnus pedunculatus, though found in several widely 

 separated places on the English and Irish coasts, is nowhere 

 very common, and thus recommends itself by its rarity, as 

 well as its beauty, to the collector. Few objects indeed 

 are more attractive to the eye of a botanist than a fine 

 frond of this species, as it waves its feathery branches in 

 the water ; but were the use of the dredge more general 

 with algologists, this, and many other deep-water plants, 

 would probably cease to be regarded as of rare occurrence; 

 and we should be better acquainted with their habits, and 

 the exact localities which they frequent. Most of the 

 specimens now collected, are washed up by the tide, fre- 

 quently in an imperfect, or decaying condition ; or picked 

 out of fishermen's nets, in the meshes of which they get 

 entangled and torn. If raised by the dredge they wonld 

 not only be found more perfect, but in far greater plenty. 



X. CARPOMITRA. 



22. Cabrerse (Cabrera's Carpornitrd) ; frond irregularly dichoto- 

 mous, linear, narrow, flat, midribbed; branches here and there 

 constricted, Ktz. Phyc. Gen. p. 343. (Atlas, PL VI. Fig. 22.) 



Sporochnus Cabrerse, Ag. Fucus Cabrerse, Clemente. 

 Hab. Cadiz. South of Ireland and in Plymouth Sound. Ex- 

 tremely rare. 



