GENERAL SUMMARY 305 



haploid mycelium {Ab) was converted into a diploid mycelium by the 

 diploid inoculum {AB) + (ab) but not by the haploid inoculum {AB) or 

 by the haploid inoculum {ab). Why, in illegitimate combinations, a 

 diploid mycelium is superior to either of its two haploid components in 

 . diploidising power remains to be determined by further investigation. 



The diploidisation of a haploid mycelium of Coprinus lagopus by a 

 diploid mycelium in a legitimate combination must often take place 

 under natural conditions in dung-balls and is an advantageous pheno- 

 menon in that it increases the amount of diploid mycelium and the 

 chances that diploid fruit-bodies instead of haploid will be produced. 



The biological significance of conjugate nuclei in the Basidiomycetes 

 and the Ascomycetes has been discussed. 



The complete diploidisation of any multicellular and multinuclear 

 hymenomycetous haploid mycelium through the agency of a single 

 nucleus or relatively few nuclei derived from a haploid mycelium of 

 opposite sex or from a diploid mycelium containing nuclei of opposite 

 sex is absolutely dependent on the formation of conjugate nuclei. 



The organisation of the nuclei in conjugate pairs (w)-f (w) instead of 

 as isolated nuclei (2n) in the diploid mycelium and fruit-body of the 

 Hymenomycetes results, it is true, in delaying the fusion of nuclei of 

 opposite sex until the basidia come into existence, but it has the great 

 advantage that, in the diploid mycelium, each member of a pair of 

 conjugate nuclei retains its identity, so that one member of a pair can 

 divide independently of the other member of the pair whenever such a 

 division is able to promote the diploidisation of a haploid mycelium. 



In the light of what is actually known concerning the diploidisation 

 process in the Hymenomycetes, suggestions have been put forth as to 

 how diploidisation proceeds in the Uredineae, the Ustilaginaceae, the 

 Tilletiaceae, the Exoascaceae, the Pyrenomycetes, and the Discomycetes. 



VOL. IV. 



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