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OOGENESIS IN SAPROLEGNIA. 



CONTRIBUTIONS FROM THE HULL BOTANICAL LABORATORY. 



XLVI. 



Bradley Moore Davis. 

 {Concluded fro7n p. 240) 



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THEORETICAL CONSIDERATIONS. 



The writer has once before (Davis, 1900) treated a number 

 of topics suggested by recent studies on the Phycomycetes. 

 The advances in this field of research, and also among the 

 Ascomycetes, have been significant, and we seem to be nearing 

 a point where much clearer conceptions of morphology and 

 phylogeny may result. In this paper we shall take up a number 



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of considerations suggested by this and other investigations 

 since 1900, and for convenience they will be grouped under 

 headings as follows : 



1. Homologies of the coenogamete. 



2, Origin and evolution of the coenogamete. 



3. Pyronema and coenogametes among the Ascomycetes. 



4. Phylogeny of Phycomycetes and Ascomycetes. 



5. The nucleus of Phycomycetes in ontogeny. 



HOMOLOGIES OF THE COENOGAMETE. 



The writer suggested the term '* coenogamete" (Davis, 1900) 

 as appropriate to fusing multinucleate masses of protoplasm 

 whose individual nuclei are actually or potentially sexual. Stev- 

 ens's first paper (1899) ^n Albugo Bliti really opened the field in 

 its newer cytological aspects. Since then Harper (1900) has 

 described for the ascomycete Pyronema strikingly similar con- 

 ditions, as has also Juel (1902) for Dipodascus ; and from the 

 studies of Gruber ( 1 90 1) we know more about the sexu 

 processes in the Mucorales. Harper's results will be considered 

 in a special connection. It is important at the outset that we 

 understand clearly the homologies of the coenogamete. 



Are all coenogametes homologous with one another, and from 



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