n6 



ASCOMYCETES AND RHODOPHYCEvE. 



fuse, but this fusion does not, as previously stated for Sphczrotheca, 

 represent a sexual process. 



It will thus be seen that the process of fecundation in Pyronema 

 consists in the union of multinucleated gametes and in the fusion of 

 their nuclei respectively in pairs. Here as in all other plants, whether 

 possessing uninuclear or multinuclear gametes, the fact of prime 

 importance is the fusion of the sexual nuclei, the cytoplasm playing 

 perhaps an incidental and secondary role. The fusion of numerous 

 pairs of sexual nuclei in the egg-cell is after all not so remarkable since 

 the significance and final result is the same as in the case of uninuclear 

 gametes. We may upon strong grounds conclude with Harper that 

 " this aggregation of nuclei at the time of fertilization seems to be 

 simply a provision for the pairing of male and female nuclei with the 



' ' 



FIG. 44. Group of 3 pairs of sexual organs of Pyronema in surface view. (After Harper.) 



greatest certainty and despatch." The cell, considered as a morpho- 

 logical and physiological unit, is just the same no matter whether it 

 possesses one or many nuclei, and in this respect there seems to be no 

 good reason for regarding a "coenocyte " as a tissue. 



' BATRACHOSPERMUM. 



As representing the sexual process in the Rhodophycece I have 

 selected Batrachospermum and Dudresnya. Batrachospermum is 

 selected on account of the comparative simplicity of the spore-fruit 

 development, and because the fusion of the sexual nuclei, as observed 

 by Osterhout (1900), leaves not the slightest doubt as to the exact 

 nature of a sexual reproduction. The classical object, Dudresnya, 

 affords an illustration of a complex series of phenomena following 

 fecundation, which has, until recently, been regarded as representing 

 several separate sexual acts. 



