SIGNIFICANCE OF CONJUGATE NUCLEI 291 



these pairs of nuclei move into the ascogenous hyphae where they 

 undergo conjugate nuclear division which comes to an end when 

 a sufficient number of ascus ceils has been produced. We thus see 

 that in the fruit-bodies of the Pyrenomycetes and Discomycetes, 

 just as in the vegetative myceUa of the Basidiomycetes, the nuclei 

 of opposite sex are attracted to one another to the extent of 

 forming pairs which can divide conjugately but are inhibited from 

 fusing with one another until the cells which are to form the spores 

 have come into existence. 



In a number of species of Pyrenomycetes and Discomycetes, 

 the oogonium contains numerous nuclei and receives numerous 

 nuclei from the antheridium ; and there is therefore a possibiHty 

 that the conjugate nuclear arrangement in these fungi may be 

 correlated, as it is in the Hymenomycetes, with the pairing of 

 unequal numbers of nuclei of opposite sex. This possibiUty will 

 now be discussed with special reference to Pyronema confluens. 



The sexual organs of Pyronema confluens are of large size ; and, 

 according to Claussen,i the ripe ascogonia and antheridia each 

 contain some hundreds of nuclei. Hence we may assume that 

 there is usually an inequality in the number of nuclei contained 

 in an antheridium and its associated ascogonium. Claussen points 

 out that the number of ascogonia which may unite with a single 

 antheridium varies from one to three, and that this alone affords 

 evidence that often there must be an inequaUty in the number of 

 male and female nuclei which come together. Since, as we may 

 assume, the number of male nuclei which enter an ascogonium is 

 not equal to the number of female nuclei already present there, it 

 might at first seem that, after the pairing of the male and female 

 nuclei in the ascogonium has taken place, a certain number of 

 nuclei, all male or all female, must remain unmated ; but, in view 

 of what happens in the diploidisation process in the Hymeno- 

 mycetes, it is not difficult to imagine how surplus male or female 

 nuclei might be provided with mates. Let us assume, for example, 

 that one hundred male nuclei derived from an antheridium that is 

 united with the trichogynes of two or three ascogonia make their 



1 P. Claussen, " Zur Entwicklungsgeschichte der Ascomyceten. Pyronema 

 confluent;' Zeitschrift J. Botanik, Bd. IV, 1912, pp. 1-64. 



