276 BRITISH SEA-WEEDS. 



to the extent of many inches, without the least lacera- 

 tion." C. arenosa grows on sandy shores between the 

 tide-marks in Scotland and Ireland. It differs from the 

 other species of the genus in the greater length of its 

 cells. 



Genus CXIY. CYTOPHORA. 



" Filaments membranaceous, interwoven, attached or 

 floating ; cells oblong, with here and there a pair of swollen 

 discoloured cells." (Dr.J.E. Gray). — Cytophora, from the 

 Greek kutos, a cavity, andpJiero, to bear. 



This genus contains a single British species, which was 

 formerly Conferva litorea. 



Cytophora litorea. The shore Cytophora. 



Threads robust, rigid, crisped, about four inches long, 

 sometimes angularly bent, growing in loosely interwoven 

 layers of considerable extent, which either float or spread 

 themselves over mud, etc. ; cells about once and a half as 

 long as broad. At irregular intervals of the thread a pair 

 of cells, larger than the others, unite into a spindle-shaped 

 knot, in which a dark-coloured endochrome is developed. 



This plant grows on muddy shores between the tide- 

 marks, in the estuaries of rivers, and in salt-water 

 ditches. It is a summer annual. 



Genus CXV. HORMOTRICHUM. 



Frond a simple or slightly branched, hair-like, gelatin- 

 ously membranaceous filament, attached by its base, and 

 formed of very short cells, which have thick, soft walls, and 

 are filled with green, granular endochrome, whence darker- 



