290 BRITISH SEA-WEEDS. 



then furnished with closely -pressed pseudo-branches, grow- 

 ing in dark-green, velvety layers of indefinite extent ; endo- 

 chrome dark-green, distinctly marked with close striae. 



Genus CXXII. ARTHRONEMA. 



" Filaments simple, of equal diameter, united together 

 longitudinally." {Dr. J. E. 6rm?/.)— Arthronema, from the 

 Greek arthron, a joint, and nema, a thread. 



The marine species of this genus were also formerly 

 Calothrices. 



Arthronema hydnoides. Mydnum-like Arthronema. 



Threads growing in flat, dark olive-green patches, of 

 considerable extent, elongated, slightly curved, blunt, inter- 

 woven below, their points massed together in erect tooth- 

 like bundles ; endochrome dark-green, distinctly striate at 

 short intervals, surrounded by a broad, transparent, yellowish 

 border. 



This species grows on clayey seashores, near high- 

 water mark, and is not uncommon. The threads are 

 spuriously branched, or rather attached one to another, 

 generally a small thread to a large one, by their sides 

 near the tip in a longitudinal series. 



Arthronema csespitula. The cushioned Arthro- 

 nema. 



Threads growing in close, convex, blackish-green tufts, 

 curved, twisted, soft, blunt, attached to each other longi- 

 tudinally ; endochrome distinctly striate at short intervals, 

 surrounded by a narrow, transparent border. 



