HOW TO KNOW THE SEAWEEDS 



superficia.} 



^sporangia, X x.^« 



/) OJ) ^germination 



teira,spores 



carpospores 



non-moiile 

 sperrnatioL 



carpo^onia 



branch 



cijstocarp feriili-taiion 



'^^^^^^ development ^^ •' 



carposporophyte 

 in Q ^ametophyte 



Fig. 12. Diagram of the life cycle of Gracilaria. 



Again as a broad generalization it may be said that a large ma- 

 jority of the Red Algae have an alternation of not two, but three gen- 

 erations, namely a sporophyte and a gametophyte generation which 

 are isomorphic, and a carposporophyte generation which remains at- 

 tached to and, in a sense, parasitic on the gametophyte generation. 

 Briefly, a macroscopic sporophyte plant produces non-motile asexual 

 spores, usually tetraspores, which germinate to produce separate male 

 and female gametophyte plants. The male plants produce non-motile 

 sexual cells (spermatia) which are freed and lodge against and fuse 

 with the female sex organ (carpogonium) on the female plant. As a 

 result of gametic union which may occur in a variety of ways, a new 

 generation begins development in or on the female gametophyte. This 



24 



