260 BRITISH SEA-WEEDS. 



the zoospores are developed. — Cladophoea, from the Greek 

 klados, a branch, and pTioreo, to bear. 



A very large number of species are included in this 

 genus : some of them are marine^ and others grow in 

 brackish or in fresh water. Their specific characters 

 are not well defined, and even the limits of genus have 

 yet to be authoritatively traced. Several modes of 

 grouping the species into new genera have been pro- 

 posed; but none of these are sufficiently established 

 to be admissible into a popular work. I have, there- 

 fore, retained the name Cladophora, and contented my- 

 self with arranging the species according to the most 

 recent and best-defined systems. 



^ Cladophora rapestris. The rock Cladophora. 



Fronds densely tufted, rigid, shrub-like, from three to 

 nine inches long, of a dark-green colour ; branches oppo- 

 site ; branchlets awl-shaped ; cells about three times the 

 length of their diameter. 



This species is annual, and grows during summer and 

 autumn on rocks between the tide-marks, and iu deep 

 water. It is common all round the British coast, and 

 may be readily recognised by the hard, rigid texture 

 and dark-green colour of its fronds. Dr. Harvey 

 writes — "The process of cell-division is well illustra- 

 ted in this species, and may be observed even in dried 

 specimens, so perfectly does the endochrome recover 

 its form. The cells of the middle portions of the 

 branches divide, as well as those of the younger ra- 

 muli, and consequently consecutive cells are found of 

 various lengths." 



