Zbti BRITISH SEA-WEEDS. 



meter, when young cylindrical, becoming elliptical as the 

 zoospores are developed. 



This species is placed by Dr. Gray in a new genus, 

 under the name Vagabundia, characterized as follows : 

 — " Frond green, forming tufts, branched ; cells elon- 

 gate, subcylindrical, the cells of the stem becoming 

 swollen and converted into sporangia." C. fracta grows 

 in brackish or fresh water, and is common. In the 

 earlier stages of its growth it is of a grass-green colour, 

 but becomes darker as it approaches maturity. It does 

 not adhere closely to paper. 



Cladophora arcta. The straight Cladophora. 



Fronds from two to four inches long, growing in dense 

 tufts, at first only slightly tangled at the base, eventually 

 matted into a sponge-like, circular mass ; branches numer- 

 ous, erect, straight, furnished below with root-like fibres ; 

 branchlets opposite or secund, blunt at the tip, their axils 

 very acute ; cells from one to ten or twelve times the 

 length of their diameter, the increase of length being gra- 

 dual from the base to the tip of the frond. 



This and the two following species are placed by 

 Kiitzing in his section Spongomorpha, and Dr. Gray has 

 founded a new genus, Spongiomorpha, in which he has 

 associated them with C. Gattym, and I am inclined to 

 think that C. repens might be also included, as it has the 

 root-like fibres, and is otherwise similar. Dr. Gray gives 

 the characters of Spongiomorpha as follows : — " Frond 

 erect, forming tufts; branches virgate, clichotomous, sub- 

 simple, with root-like fibres ; cells oblong, filled with 

 granular endochrome, becoming zoospores, marine." 

 C. arcta grows on rocks in tide-pools, during the greater 



