80 THE MARINE BOTANIST. 



independently of these microscopic characters^ tlie 

 genera of each subdivision differ much in outward 

 character ; in Cladostephus and Sphacelaria the 

 texture is firm and rigid, adhering very imperfectly 

 to paper, while in Ectocarpus and Myriotrichia the 

 species are often smooth and soft as floss silk, and 

 firmly adhere to paper. The Ectocarpi are a dif- 

 ficult genus, and it is necessary for their dis- 

 crimination to have recourse to the microscope, 

 and even then they are not easily distinguished 

 when without fruit. Myriotrichia comprises two 

 small species, parasites ; the one M. clavseformis 

 on Chorda lomentaria; the other M. filiformis on 

 the same plant, and occasionally on Asperococeus 

 echinatus; this latter is much the most abundant 

 kind, and grows on the Chorda, when growing in 

 shallow pools, exposed to the light. The sup- 

 posed new species of Ectocarpus ^figured under the 

 name of E. tessellatus in the first volume of the 

 '^ Naturalist," has proved on further investigation 

 only a variety of E. fasciculatus. 



