No. 525] SEXUAL BEPRODUCTION IN ALGJE 



.V2D 



to be tetraspore mother-cells on sexual plants, but in this 

 material the apparent tetrasporangia failed to mature 

 tetraspores, the cleavage furrows proceeding only a short 

 distance into the mother cells while the nuclei either re- 

 mained undivided {Polyslphonia) or produced groups of 

 several nuclei (Griffithsia). Thus such cytological evi- 

 dence as we have on these irregularities indicates them 

 to be abnormal developments. Examples of apogamy 

 and apospory are now recognized as by no means uncom- 

 mon in the hight'r group- of plants exhibiting alternation 

 of generations, and it will not be at all surprising if such 

 phenomena or related irregularities of life history are 

 found among the Rhodophycea\ Such peculiarities must 

 of course be thoroughly studied to determine whether or 

 not they will prove to be the exceptions that support the 

 rule. The investigations of recent years on apogamy 

 and apospory in the pteridophytes have in no way weak- 

 ened the acknowledged alternation of generations in that 

 group. 



A very interesting problem is presented in the phe- 

 nomenon described by Osterhout 17 of the germination of 

 the tetraspores of AgardhieUa tenera {Rhabdonia tenera) 

 while still imbedded in the tissue of the parent plant. A 

 peculiarity of this development is the behavior of the 

 group of tetraspores as a unit, so that all four cells enter 

 into the formation of a sporeling. It is important to 

 note that the sporelings are very commonly sexual plants, 

 as would be expected from the germination of normal 

 tetraspores. It seems quite possible that the occasional 

 tetrasporic shoots reported by this author are products 

 of a tetraspore mother-cell in which the reduction mitoses 



