156 SEA-WEEDS. 



a remarkable appearance. In preserving speci- 

 mens of the fucus, care should be taken to procure 

 one on which this parasite exists, as it is almost 

 peculiar to the knobbed fucus, and so frequent 

 as to seem almost to belong to it. 



There is very great beauty in some of these 

 Polysiphoneae, with their red or dark purple tufts 

 of filaments. They were named "many siphoned," 

 in reference to the numerous little canals by 

 which the coloured matter is carried from one end 

 to the other of the plant; and this colouring 

 matter seems greatly affected by circumstances. 

 When growing, these plants are brown, but when 

 plunged in fresh water they become purple or 

 pink. Several of the species are common, but all 

 too much alike to admit of popular description. 

 The Bushy Polysiphonia (Polysiphonia fucoides) 

 is a frequent plant on rocks, and on other sea- 

 weeds. It is from four to six inches long. The 

 main stalk, which is about as thick as a coarse 

 thread, is very rigid and dark at the lower part, 

 and very bushy with numerous branches above. 

 The superior branches are of a dull reddish-brown, 

 and rather flaccid. Dr. Johnston observes of this 

 species, that though subject to some variety, the 

 practical botanist recognises it by the dark dull 

 colour of its rigid stalk, its elongate flattened 

 form, and by the bushiness of its superior branches. 



Another plant of this genus, the Lobster-horn 

 species (Potysvpkomq elongata], is a firm, though 

 slender sea-weed, with a main stem as thick as 

 twine, and branches which somewhat resemble 

 the horn of the shell-fish from whence it has its 

 name. It is slightly marked with rings on its 

 stem and branches. It is very common on rocks, 



