THE ALGAE 



181 



Alternation of Generations in the Rhodophyceae 

 In the Algae the life history may include only one type of vegetative plant, 

 or there mav be two separate kinds of vegetative plants, the one producing 



Fig. 173. — Corallina officinalis. A, Longitudinal section of a young tetrasporangial 

 conceptacle with voung sporangia, not yet transversely divided. B, Young 

 tetrasporangium before meiosis, showing stalk cell. On the right a sporangia! 

 rudiment. C, Tetrasporangium in division after meiosis. {After Sumeson.) 



gametes and the other producing non-sexual spores or zoospores. In the 

 latter case the plants may be morphologically identical or they may be 

 different in form, sometimes so much so that they were once considered to 

 belong to distinct genera, as in CutJeria. 



A life-history of the first category, in which there is only one type of 

 vegetative plant, is said to be haplobiontic. Examples of this are Chlamy- 



