EFFECT OF DIPLOID ON HAPLOID MYCELIA 255 



on a haploid mycelium in a manner different from that of either of 

 the two haploid mycelia which produced it ? 



Four haploid myceha (AB), (ab), (Ab), and (aB) and two diploid 

 myceUa {AB)-]-{ab) and {Ab)-\-{aB) required for making the experi- 

 ments were obtained as follows. A large haploid mycelium (AB) 

 was inoculated with a tiny fragment of a diploid mycelium 

 {AB)-i-{ab). The (AB) mycelium became diploidised (as indicated 

 by the appearance of clamp-connexions and a change from the 

 haploid to the diploid mode of branching in all the peripheral 

 hyphae) in about three days. A piece of the diploidised myceUum 

 was placed on sterilised horse dung where it grew well and soon 

 produced fruit-bodies. From one of the fruit-bodies a spore- 

 deposit was obtained. Ten of the spores of this spore-deposit, 

 after being sown on dung-agar, yielded as many haploid myceUa. 

 These ten myceh'a were then paired in all possible ways (c/. Table III, 

 p. 236) with the result that it was found that in the ten mycelia 

 there were representatives of all the four possible kinds (AB), (ab), 

 (Ab), and (aB). Four of these mycelia, one of each of the kinds 

 (AB), (ab), {Ab), and (aB), were chosen as the four haploid mycelia 

 required for making the experiments about to be described. Pieces 

 of these four mycelia were then paired on two dung-agar plates in 

 the combinations (AB) X (ab) and (^6) X (aB) ; and thus the two 

 required diploid myceha {AB)-\-{ab) and {Ab)-\-{aB) were obtained. 



The four haploid mycelia (AB), (ab), (Ab), and (aB) and the 

 two diploid myceha {AB)~\-{ab) and {Ab)-\-{aB) obtained in the 

 manner just described were grown separately on as many dung-agar 

 plates. As soon as they had attained a sufficiently large size they 

 were used to inoculate twenty-four freshly-poured dung-agar plates : 

 six plates were inoculated with the (AB) mycelium, six with the 

 (ab) mycelium, six with the (Ab) mycelium, and six with the (aB) 

 mycehum. The twenty-four plates were then placed under glass 

 covers and left there for a few days until each of the twenty-four 

 mycelia had attained a diameter of about 4-5 cm. Each of these 

 twenty-four large mycelia was then inoculated at its periphery 

 with a small fragment of one of the mycelia (AB), (ab), (Ab), (aB), 

 {AB)^{ab), and {Ab)-ir{aB) which were growing in the plates 

 referred to at the beginning of this paragraph. 



