7 o TEXT-BOOK OF FUNGI 



of fertilisation, from a modern cytological standpoint, of 

 more than about twenty species, and even among these, 

 the crucial evidence, the fusion of nuclei, is in some 

 instances only assumed ; hence critical discussion and 

 philosophical speculation are equally unsafe. 



Wager points out that three methods of fertilisation 

 occur in the Peronosporeae alone. (i) Uninucleate 

 oosphere, binuclear fusion, and uninucleate oospore (P. 

 parasiticd). (2) Uninucleate oosphere, binucleate fusion, 

 and multinucleate oospore (C. candidus, C. portulacae, and 

 P. ficariae). (3) Multinucleate oosphere, multinuclear 

 fusion in pairs, and multinucleate oospore (C. bliti}. 



Fisch states that in Pythium the nuclei of the oogonium 

 fuse together to form one female nucleus, and that the one 

 nucleus in the antheridium is also probably the result of 

 fusion of several nuclei. In the process of fertilisation the 

 male nucleus enters the oogonium and fuses with the 

 female nucleus to form the first nucleus of the oospore. 

 If this account is corroborated, it will constitute a fourth 

 type. 



The difference of opinion respecting the occurrence of 

 fertilisation in the Saprolegniaceae has at last been set at 

 rest by the investigations of Trow, who has demonstrated 

 an undoubted sexual process in several members of the 

 family. The following is an abridged account of his re- 

 searches on Achlya debaryana of Humphrey ( = Achfya 

 polyandra, De Bary). The antheridia and cogonia 

 are multinucleate; the nuclei in both organs divide 

 indirectly, and there are apparently eight chromosomes 

 at this stage. Some of the nuclei in both organs undergo 

 a second division in which the number of chromosomes is 

 apparently reduced to four. The number of nuclei in the 



