2o6 RESEARCHES ON FUNGI 



experiment), the originally haploid mycelium (ab) had become about 

 2-5 cm. in diameter, and now clamp-connexions were seen to be 

 present on all its peripheral hyphae. 



The experiment just described was repeated, with the same 

 result : the haploid mycelium (ab) when mated with the diploid 

 mycelium {AB)-\-{ab) developed clamp-connexions on all its leading 

 hyphae by the end of five days from the time of pairing the two 

 mycelia. 



The results of the two preliminary experiments just described 

 indicated very clearly that a diploid mycelium {AB)-\-{ab) is able 

 to diploidise a haploid mycelium {ab) when brought into contact 

 with it. 



Positive results having been obtained by pairing a haploid with 

 a diploid mycelium of Coprinus lagopus, the way was opened for 

 the setting up of further series of experiments which will now be 

 described. 



(2) The haploid mycelium large, the diploid small and set at the 

 periphery of the haploid. In the preliminary experiments ordinary 

 Petri dishes, 10 cm. in diameter, were employed, and the two pieces 

 of mycelia used for inoculating the dung-agar were of equal size. 

 A change in the mode of experimentation was now made. Wider 

 Petri dishes, 15 cm. in diameter, were employed, and a very 

 large haploid mycelium was paired with a very small diploid 

 mycelium. 



Two pieces of the haploid mycelium No. 5 {ab) were removed 

 from a stock dung-agar culture and each one was set in the middle 

 of the dung-agar in a freshly-poured large Petri dish ; and the two 

 myceUa, one in each dish, were allowed to grow for more than a 

 week. At the end of eight days the diameter of one of the two 

 mycelia was 5-2 cm., and at the end of nine days the diameter of 

 the other was 5-4 cm. When the two {ab) mycelia had attained 

 these diameters, a tiny mass of aerial hyphae of the diploid mycelium 

 produced from the combination No. 10 X No. 5, {AB)-\-{ab), 

 scarcely larger than a pin's head, was placed at one spot on the 

 dung-agar in each of the two dishes within 2-3 mm. of the periphery 

 of the large mycelium {ab). The relative sizes and positions of the 

 two myceha resembled ( 1 ) at the beginning of the experiment those 



