i86 RESEARCHES ON FUNGI 



happen to unite, then through the openings made by the first few 

 hyphal fusions nuclei pass from one mycehum into the other 

 mycelium, conjugate pairs of nuclei are soon estabhshed in both 

 mycelia, and the mycelial haplophase quickly changes into the 

 diplophase. 



In the mycelium of the homothalhc Hymenomycetes, e.g. 

 Coprinus sterquilinus and C. stercorarius , the transition from the 

 haplophase with isolated nuclei to the diplophase with conjugate 

 nuclei is not necessarily preceded by the fusion of two hyphae of 

 the same thallus, for it seems to take place in successive cells of the 

 same hypha by means of some re-arrangement of the nuclei. 

 However, it is possible that very young mycelia of homothalhc 

 Hymenomycetes, while still in the haplophase, may unite with one 

 another and that under such circumstances a nucleus of one 

 mycehum may be transferred to the other, with the result that 

 conjugate pairs of nuclei come into existence and the diplophase is 

 initiated ; but this, so far, has not been actually observed. What 

 is certain is that, for the beginning of the sexual act by the formation 

 of conjugate nuclei, heterothaUic Hymenomycetes require at least 

 one hyphal fusion between two haploid mycelia of opposite sex, 

 whereas homothalhc Hymenomycetes do not require a hyphal 

 fusion of any kind. 



The freedom and rapidity with which any two mycelia of the 

 same hymenomycetous species fuse with one another where they 

 come into contact in the same substratum is a prime factor in making 

 possible that social organisation which is so marked a characteristic 

 of the vegetative parts of the Hymenomycetes and of other Higher 

 Fungi. 



