SEA WEEDS 379 



with dense matted branches and spherical pods arranged either 

 opposite to one another or to a branchlet ; and E. Mertensii, a 

 pretty species that grows on muddy rocks, freely branched but not 

 matted, and having pods enclosed by the branchlets. The last 

 species is rare, but may be found in Cawsand Bay and a few other 

 localities about Plymouth Sound. The genus includes several other 

 species, but all these are more or less rare. 



In the genus Myriotrichia we have two parasitic species with 

 fragile, hair-like, jointed fronds bearing simple straight branches 

 that are covered with transparent fibres. In these the spore-cases 

 are rounded and transparent, and arranged along the main threads ; 

 and the dark olive spores are readily visible within. In M.fiUformis 

 the branchlets are short, and clustered at intervals, thus giving a 

 somewhat knotted appearance to the threads, and both branches 

 and branchlets are covered with long fibres. The other species 

 M. clavceformis is very similar, but may be distinguished by the 

 arrangement of the branchlets, which are not clustered at intervals, 

 but are distributed regularly, and are longer towards the tip of the 

 frond, giving the appearance of minute fox-brushes. 



The genus SpTiacelaria contains several British weeds with rigid 

 branched and jointed fronds, most easily distinguished by the tips 



FIG. 263. Sphacelaria cirrhosa FIG. 264. Sphacelaria, plumosa 



of the branches, which are flattened, contain a granular mass, and 

 have a withered appearance. S. cirrhosa forms hair-like tufts of 

 slender fibres with closely-set branches on small weeds, the tufts 

 varying from a quarter of an inch to over an inch in length. The 

 fronds are naked at the base, and the spore-cases, which are globular, 

 are arranged on the branches. S.filicina is, as its name implies, of 

 a fern-like appearance, but is very variable in form. Its fronds vary 

 from one to three inches in length, and the spores are arranged 



