240 SEAWEEDS 



sation is the same in this genus as in Dudrcsnaya 

 (Fig. 81). The carpogonial branches and the cor- 

 responding but more numerous branches that bear 

 the auxiliary cells, are found together in special 

 fertile portions of the cortex of the thallus. After 

 fertilisation, this cortical tissue, having undergone 



FIG. 82. Polyides rotundus. a, procarp with trichogyne and ooblastema ; 

 b, ooblastema filament fertilising auxiliary cell highly magnified. (After 

 Thuret and Bornet.) 



considerable development, contains close together 

 numerous gonimoblasts, nearly all the cells of which 

 eventually give rise to carpospores. 



Squamaricce. 



The thallus of the Squamariece is commonly minute 

 and encrusting or consists of flat foliar expansions of 

 tissue, in most cases encrusted with carbonate of lime. 

 In this case, as in Polyidcs, the carpogonial branches 



