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. IQ03] OOGENESIS IN SAPROLEGNIA 327 



protoplasm. The coenogamete is as much an individual cell as 

 the uninucleate gamete, and distinctions can no more be drawn 

 between these two structures than between the adjacent uninu- 

 cleate and multinucleate cells of many plants (Chara, Rhodo- 

 phyceae, etc.). In view of its structure and behavior the term 

 *' coenogamete " seems to the writer appropriate. 



PVRONEMA AND COENOGAMETES AMONG THE ASCOMYCETES. 



Harper's (1900) investigation of Pyronema has established a 

 condition in the Ascomycetes very similar to that among the 

 Phycomycetes. Pyronema has as conspicuous a coenogamete 

 I as the Mucorales or Albugo Bliti. Its peculiarities do not affect 



the essential cytological structure of the fusing multinucleate 

 masses of protoplasm whose gamete nuclei unite in pairs, as in 

 Albugo Bliti and probably in the molds. The sexual apparatus of 

 Pyronema differs from the molds chiefly in the development of 

 that specialized structure the conjugating tube (trichogyne). 

 This organ is manifestly of advantage because it effects a union 

 with the antheridium, and probably, as Harper suggests, repre- 

 sents the same sort of outgrowth from a sexual element as a 

 trychogyne. The nuclei in the conjugating tube break down, 

 and the structure 'finally becomes merely the channel through 

 which the protoplasm from the antheridium flows into the oogo- 

 nium. This movement of the protoplasm \s very similar to 

 Albugo Bliti, and the resemblance is carried still farther in the 

 distribution and fusion of the gamete nuclei in pairs throughout 

 the oogonium. The ''receptive papilla" of Albugo is developed 

 from the oogonium, and the conjugating tube in Pyronema may 

 be considered an elaboration of such a growth tendency. Peri- 

 plasm is lacking in Pyronema, but the mass of nucleate proto- 

 plasm that passes into the conjugating tube may relieve the 

 oogonium of those conditions that result in the extensive degen- 

 eration of potential gamete nuclei in Saprolegnia or the somewhat 

 similar conditions affected by the differentiation of a periplasm 

 in the Peronosporales. 



It is not to be supposed that the coenogametes of Pyronema 

 are closely related to those of the Mucorales or the Perono- 

 sporales, excepting as all of these structures are the homologues 



