202 SEAWEEDS 



layer of protoplasm covers them in turn. The cords 

 which thus perforate the closing membrane establish 

 a connection between adjoining cells, and though they 

 do not admit of migrations of cell-contents in bulk, 

 they may be used for the transference of dissolved 

 substances. However, it is supposed that their main 

 function is to transmit dynamic influences, while the 

 plates are the receivers of such stimuli. 



While the composition of the thallus of the Ehodo- 

 phycece is effected typically by the congenital union 

 of cell-filaments in which subsequent intercalary 

 divisions do not occur, it happens in isolated cases 

 that such divisions occur in an exceptional manner. 

 They occur with regularity in certain Corallines, and 

 in the genus Nitophyllum and its immediate allies, so 

 far as the latter have been studied in this respect. 



As has been said, very diverse forms of thallus 

 occur among the Rhodophycece, and these forms give 

 us no definite clue to the systematic position of any 

 particular form, since there may be associated very 

 diverse formations of thallus with one common plan 

 of formation of fruits, and a similar formation of 

 thallus with diverse fruit characters. 



The Rhodophyccce are sexually reproduced by male 

 cells produced in antheridia which fertilise female 

 cells called carpogonia. The antheridia are of very 

 various forms, always giving rise superficially to the 

 special male cells which contain each a single non- 

 motile pollinoid. These male cells are formed in 

 great numbers together, and they originate from the 

 terminal cells of longer or shorter branches of the 

 thallus-filaments (Fig. 62, a). The clusters of such 



