RED ALGAE 389 



spore-formation follow (Fig. 327). This is the leading character of 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 Nemalion, which is one of the simplest 

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

 tetraspores are found, in the production of which reduction of chromosomes 

 has been demonstrated. The nuclear cycle has been fully worked out 

 in Polysiphonia violacea, in which the tetraspores and sexual organs are 

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

 inferred that 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 (gametophyte). 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 Dictyota, and questions of the origin of alternation in the Red 

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



