EFFECT OF DIPLOID ON HAPLOID MYCELIA 207 



of the two mycelia shown in Fig. 124 and (2) one day later those of 

 the two mycelia shown in Fig. 120. 



In both of the dishes it was observed that the haploid 

 mycelium {ab) became progressively diploidised by the diploid 

 niycehum {AB)-\-{ab). 

 The clamp-connexions 

 on the peripheral hy- 

 phae of the (ab) mycel- 

 ium were first observed 

 on each side of the 

 {AB)+{ab) mycehum ; 

 and, at the end of four 

 days after pairing, the 

 (ab) mycelium was 

 found to have clamp- 

 connexions on the side 

 farthest away from the 

 {AB)+{ab) mycelium 

 and therefore to have 

 become completely 

 diploidised. 



Thus it was proved 

 that a very tiny piece 

 of a diploid mycelium 

 {AB)-i-{ab) is able to 

 convert a very large 

 haploid mycelium (ab) 

 into a diploid myce- 

 lium. 



(3) The haploid mycelimn large, the diploid small and set in the 

 centre of the haploid. It seemed possible that the diploidisation of 

 the haploid myceUa in the two series of experiments already described 

 might have been due to nuclei travelling from the diploid mycelium 

 through the peripheral zone of the haploid mycelium and through 

 this zone only. To find out whether or not a diploid mycehum can 

 be efiEective through the older portions of a large haploid mycelium 

 the experiment now to be described was made. 



Fig. 120. — Coprinus lagopus. Method of mating a 

 large haploid mycelium and a small diploid my- 

 celium. The centre of a large Petri dish containing 

 cleared dung -agar was inoculated with a tiny mass 

 of aerial hyphae of a haploid myceliimi {ab). No. 6 

 of Table I. Eight days later, this mycelium had 

 attained a diameter of 4-8 cm. It was then 

 inoculated at its periphery with a tiny mass of 

 aerial hyphae of a diploid mycelium {AB) + {ab) 

 obtained by mating mycelia No. 6 and No. 2 of 

 Table I. The photograph was taken one day 

 after inoculation. The two mycelia have already 

 come into contact with one another and have 

 fused with one another hyphally. Shortly, the 

 diploid inocuhun (AB) + (ab) will begin to dip- 

 loidise the large central haploid myceliimi (ab). 

 Natural size. 



