212 RESEARCHES ON FUNGI 



mycelia, and that it can do this either when it comes into contact 

 with the haploid myceha one at a time or when it comes into contact 

 with them simultaneously. 



(5) The effect of age on the mating of a diploid with a haploid 

 mycelium. After the haploid mycelia Nos. 10 and 5, {AB) and {ab), 

 had been in stock for 5-6 weeks, a series of mating experiments, 

 designed to confirm the experiments already described, was under- 

 taken. In this series of experiments, for the sake of comparison, 

 matings were made not only between a haploid myceUum and a 

 diploid, but also between two haploid myceUa. 



Three haploid mycelia {AB) and three haploid myceha {ah) were 

 grown on dung-agar, each in a single large Petri dish ; and, when 

 they had attained a diameter of 4-6 cm., they were inoculated at their 

 periphery (as in the preceding experiments) as follows : 



{AB) with {AB)+{ab), 

 {AB) with {ab), 

 {AB) with {ab), 

 (a6 with {AB)-{-{ab), 

 {ah) with {AB), 

 {ah) with {AB). 



In all these six experiments, the large central haploid mycelium, 

 which eventually attained a diameter of 10 -0-12 -5 cm., became 

 progressively diploidised, and the diploidisation proceeded along its 

 periphery away from, and on both sides of, the inoculum ; but the 

 rate of change from the haploid to the diploid phase was much 

 slower than had previously been observed and, when growth ceased 

 in the plates, diploidisation of the central myceha had been com- 

 pleted only in one of the {ab) X {AB) matings. In all the other 

 five matings diploidisation had progressed only from one-half to 

 three-quarters the way around the central mycehum. There was 

 no marked difference between the effect of a haploid mycehum on 

 a haploid mycehum and the effect of a diploid mycelium on a hap- 

 loid mycehum ; but other experiments yet to be recorded will throw 

 further light on this point. 



Another set of experiments, similar to those just described, was 

 carried out a month later. Four haploid myceha were inoculated 



