254 RESEARCHES ON FUNGI 



sation of certain large haploid mycelia by certain diploid mycelia 

 in illegitimate combinations, a second series of experiments similar 

 to the first series, but starting with a new set of haploid mycelia, 

 was undertaken. 



A large haploid mycelium (AB) inoculated with a diploid myce- 

 hum {AB)-{-{ab) had become completely diploidised, and the diploid 

 myceUum, after transference to sterilised horse dung, developed a 

 fruit-body. 



Some of the spores of the fruit-body were germinated indivi- 

 dually. The monosporous mycelia thus obtained were then paired 

 in all possible combinations, with the result that they were found 

 to fall into the usual four groups (AB), {ah), {Ab), and {aB). Four 

 of these myceha, one from each group, were then used to make up 

 the two possible kinds of diploid mycelia {AB) +(a6) and (^6) +{aB). 

 Finally, a haploid mycelium was paired with a diploid myceUum 

 in each of the four possible illegitimate combinations as follows : 



{AB) X {Ab)+{aB), 

 {ab) X {Ab)+{aB), 

 {Ab) X {AB)^{ab), 

 {aB) X {AB)^{ab). 



Each of the haploid myceUa was allowed to grow until it was 

 several centimetres in diameter, and then it was inoculated at its 

 periphery with a tiny fragment of the diploid mycelium. 



The results of these experiments were even more surprising than 

 those obtained in the first series of experiments ; for, in every 

 combination the large haploid mycelium became diploidised com- 

 pletely or almost completely all around its periphery (shown by 

 diploid mode of branching and presence of clamp-connexions). 



The discovery made in the first two series of experiments that, 

 in illegitimate combinations, a diploid mycelium may sometimes 

 or often diploidise a haploid myceUum, led the writer to make a 

 third and last series of experiments which will now be recorded. 



Third Series of Experiments. This series of experiments was 

 made with a view to deciding the question raised at the end of 

 the discussion of the results of the first series of experiments : in 

 general, in illegitimate combinations, does a diploid mycelium act 



