76 BRITISH SEA-WEEDS. 



This plant is very common on our coasts, and is widely 

 distributed elsewhere. It is frequently infested with 

 parasitic algse, especially with Jania rubens. 



Cladostephus spongioses. Spongy Cladostephus. 



Fronds three to four inches high, irregularly branched ; 

 branches thick, densely covered with jointed, mostly simple, 

 branchlets. Fructification on short accessory branchlets, 

 produced in winter in the same manner as in the last 

 species. 



Dr. Harvey, in his ' Nereis Boreali-Americana/ ex- 

 presses a doubt whether these two species are distinct. 

 They differ in size and general appearance, and in the 

 arrangement of the branchlets ; but their technical cha- 

 racters are not constant. 



Genus XXXIII. SPHACELARIA. 



Frond branched, jointed, rigid, the tips of the branches 

 distended into a membrane containing a granular mass 

 called a propagulum. Fructification, egg-shaped spores, with 

 a pellucid margin, or perispore, affixed to the branches, and 

 propagula. — Sphacelabia, from the Greek spliakelos, a 

 gangrene, in allusion to the withered appearance of the tips 

 of the branches. 



This genus comprises several species, mostly natives 

 of the shores of Europe ; some of them extend to the 

 Mediterranean, and even as far south as the Cape of 

 Good Hope, while others are found in the Baltic and on 

 the shores of Greenland. 



