302 RESEARCHES ON FUNGI 



Chapter II. The term diploidisation has been introduced to desig- 

 nate the process by which a haploid cell is converted into a diploid cell, 

 or a haploid myceUum into a diploid mycelium, by the formation of 

 conjugate nuclei within the cell or within the mycelium. The diploidisa- 

 tion process is completed : in Hymenomycetes, in a haploid myceHum 

 which is converted into a diploid myceHum ; in Uredineae, in the 

 spore-bed of the aecidium ; in certain Smut Fungi, e.g. Ustilago zeae, in 

 a haploid myceUum within the host-plant ; in Exoascaceae, in a sprout- 

 conidium on the surface of the host-plant ; and, in certain Pyrenomycetes 

 and Discomycetes, in the ascogonium. 



A haploid or diploid cell is said to diploidise a haploid cell when, 

 through its agency, the latter becomes converted into a diploid cell 

 containing conjugate nuclei {n) + {n). 



A haploid or diploid myceUum is said to diploidise a haploid myce- 

 lium when, through its agency, the latter becomes converted into a 

 diploid mycelium containing conjugate nuclei {n) + {n). 



In experiments on the diploidisation process in Coprinus lagopus, 

 when a tiny fragment of a haploid or diploid myceHum has been set at 

 or just outside the periphery of a very large haploid mycelium with a 

 view to converting the latter into a diploid mycelium, the large myceHum 

 is said to have been inoculated with the tiny fragment of mycelium, and 

 the tiny fragment of myceHum is spoken of as an inoculum. 



The method of inoculating a large haploid myceHum several centi- 

 metres in diameter with a smaU haploid or diploid myceHum 1-2 mm. 

 in diameter has been introduced as an aid to the study of the 

 diploidisation process in Coprinus lagopus and other Hymenomycetes. 



The Coprinus lagopus of the author's Researches on Fungi and of 

 his pupils is identical with the Coprinus fimetarius of Mile Bensaude, 

 Kniep, Brunswik, Oort, and other workers on sex in the Hymeno- 

 mycetes. 



An individual fruit-body of Coprinus lagopus produces four sexually 

 dififerent kinds of spores, and these spores give rise to four kinds of 

 haploid myceHa with the factorial composition {AB), {ah), {Ah), and 

 {aB). By pairing {AB) with {ah) and {Ah) with {aB), it is possible to 

 obtain two kinds of diploid myceHa {AB)-\-{ah) and {Ah) + {aB) 

 respectively. 



Combinations of the type {AB) x {ah) and {Ah) x {aB) have been 

 spoken of as legitimate combinations between two haploid myceHa ; and 

 combinations of the type {AB) x {AB) + {ah) and {ah) x {AB)-^{ah) 

 have been spoken of as legitimate combinations between a haploid 

 myceHum and a diploid mycelium. 



Combinations of the type {AB) x {Ah), {AB) x {aB), {ah) x {Ah), 

 and {ah) x {aB) have been spoken of as illegitimate combinations between 

 two haploid myceHa ; and combinations of the type {AB) x {Ah)+{aB), 

 {ah) X {Ab) + {aB),{Ah) x {AB) -\- {ah), and {aB) x {AB)+{ah) have been 



