ALG^E 73 



As a rule, the fresh-water Rhodophycese are simpler 

 in structure than their marine relatives, and proba- 

 bly represent a more primitive type of structure from 

 which the others have been derived. It is not impos- 

 sible that these simple fresh-water forms may also be 

 intermediate between the green algse and the higher 

 Rhodophycese. It must be admitted, however, that, with 

 the exception of the Bangiacese, a group whose affinity 

 with the true Rhodophycese has been questioned, all the 

 fresh-water forms, although simpler in structure, are 

 typical Rhodophyceee, so far as the reproductive parts 

 are concerned. 



The motile zoospores of the brown and green algae 

 are replaced in most Rhodophycese by the so-called 

 tetraspores, formed four together in a common mother- 

 cell, much as zoospores are formed. These escape from 

 the mother-cell and form new plants at once (Fig. 19, 

 A, B). 



The sexual reproduction shows certain peculiarities 

 which are not found elsewhere in the vegetable king- 

 dom, although there are certain analogies in the fertil- 

 ization of some fungi. The antheridium (Fig. 20, C) 

 is made up of a great number of small cells which arise, 

 as short branches, very much crowded together. The 

 contents of the terminal cells escape in the form of a 

 naked, but non-motile cell, or spermatium, which differs 

 in structure from the spermatozoids of other algae, 

 mainly in the absence of cilia. So far as is known, the 

 conveyance of the sperm-cell to the female reproductive 

 organ, or procarp, is dependent upon the movements of 

 the water. 



The female reproductive organ of the Rhodophycese 



