EFFECT OF DIPLOID ON HAPLOID MYCELIA 189 



of great physiological importance in that it may permit of a diploid 

 mycelium diploidising an appropriate haploid mycelium in dnng-haWs, 

 wood, or other substrata where haploid and diploid mycelia often 

 intermingle, thus increasing the amount of diploid mycelium pro- 

 duced in the substratum and therefore also increasing the chances 

 that a vigorously fruiting mycelium giving rise to diploid fruit-bodies 

 yielding all the possible sex-groups of spores will be developed rather 

 than a feebly fruiting mycehum giving rise to haploid fruit-bodies 

 yielding but one sex-group of spores. And it further occurred to 

 me that it would be possible to test the value of the theory just 

 propounded in a very simple manner, i.e. by pairing a diploid with 

 a haploid mycelium of the same species and observing whether or 

 not the diploid mycehum is able to diploidise the haploid mycelium. 

 The mating of a diploid with a haploid mycelium in a typical 

 Hymenomycete, namely Coprinus lagopus, has, as we shall see, been 

 successfully and repeatedly accomplished. During the course of 

 the investigation, and incidentally thereto, it has been possible, for 

 the first time, to measure the minimum speed with which nuclei pass 

 through a haploid mycehum, both ( 1 ) when the haploid is mated with 

 another haploid of opposite sex and (2) when the haploid is mated with 

 a diploid containing nuclei of a sex opposite to those of its own nuclei. 

 After the experiments recorded in this chapter had been nearly 

 completed, the writer perceived that the organisation of the nuclei 

 in the diploid mycelial hyphae of the Hymenomycetes in conjugate 

 pairs is essential for the diploidisation of any haploid mycelium what- 

 soever, regardless of the kind of mycelium, haploid or diploid, which 

 may initiate the diploidisation process. In the discussion at the 

 end of this chapter, it will be emphasised that the existence of con- 

 jugate nuclei in the diploid hyphae of Hymenomycetes is correlated 

 with the multicellular and multinuclear condition of the haploid 

 mycelia which must be diploidised, and that the advantage of 

 conjugate nuclei {n)^{n) over solitary {2n) nuclei lies in this : 

 that, in any pair of conjugate nuclei, each member of the pair, 

 although constrained to act with its fellow-member in a conjugate 

 nuclear division during cell-division, yet retains its identity, so that 

 it can divide independently of its fellow-member whenever such 

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



