RED ALGAE 3S9 



spoi-e-lonuation follow (Fig. J27). This is the leading cliuracter ol the Red 

 Algae, and it is worked out in some of them with extreme complication of 

 detail in the method of transfer of the nucleus. 



In some Red Algae, such as Neinalion, which is one of the simplest 

 of them all, no other organs of propagation are known. But in most of them 

 teiraspoyes are found, in the production of ■i\'hich reduction of chromosomes 

 has been demonstrated. The nuclear cycle has been full}* worked out 

 in Polysiphonia violacca, in wliich the tetraspores and sexual organs arc 

 borne on separate plants. The carpospore on germination is diploid : it is 

 inferred tliat it produces a tetrasporic plant {sporophyte), which after reduction 

 bears tetraspores. The tetraspore on germination is haploid : it is inferred 

 that it produces the haploid sexual plant [gametophyie). The haploid nuclei 

 of spermatium and carpogonium on fusion lead to the formation of the diploid 

 carpospores : and so on. There is thus a regular alternation of tetrasporic 

 and sexual plants ; but in form these are closely alike. The case is comparable 

 with that of Dictyotn, and questions of the origin of alternation in the Red 

 Algae are raised similar to those for the Brown. (See Chapter XXXII.) 



