SIGNIFICANCE OF CONJUGATE NUCLEI 275 



another, each mycehum receives from its mate not a number of 

 nuclei equal to the number of its own nuclei, but relatively very 

 few nuclei (sometimes, perhaps, only one). 



In order to understand how it is that one or a few nuclei derived 

 from one haploid mycelium are able to bring about the diploidisa- 

 tion of another large haploid mycelium of opposite sex, it will be 

 necessary to inquire into the details of the diploidisation process 

 and to find out exactly what part conjugate pairs of nuclei play 

 therein. 



Relying on the cytological work of Lehfeldt (to which reference 

 has already been made, p. 216) and on my own observations on 

 the direct transformation of haploid hyphae into diploid hyphae 

 as indicated by the production of clamp-connexions and by a change 

 from the haploid to the diploid mode of branching {vide Fig. 133, 

 p. 238), let us endeavour to imagine the course of the diploidisation 

 process in a large haploid mycelium of Coprinus lagopus, con- 

 taining 100,000 (ab) nuclei scattered in its hyphae, after the myce- 

 lium has met with, and fused with, a single hypha of a mycelium 

 of opposite sex and has received through the hypha a single (AB) 

 nucleus. 



The (AB) nucleus, on entering the (ab) mycehum, at once begins 

 to divide and subdivide, and the (AB) nuclei so produced move 

 through the three-dimensional network of hyphae which make up 

 the (ab) mycelium. Soon, certain of the {AB) nuclei associate 

 themselves individually with certain {ab) nuclei and a number of 

 conjugate pairs of nuclei {AB)-{'{ab) become established, particu- 

 larly at the ends of the rapidly-growing hyphae in the neighbour- 

 hood of the {AB) hypha. To allow of the passage of the {AB) 

 nuclei through the {ab) network of hyphae, the simple septa of the 

 {ab) hyphae become partially or wholly broken down as {AB) 

 nuclei approach them. Whilst some of the {AB) nuclei form 

 conjugate pairs with certain of the {ab) nuclei, other {AB) nuclei 

 are moving through the {ab) mycelium away from the {AB) hypha 

 and away from the {ab) hyphae which already have come to contain 

 conjugate pairs of nuclei. These moving {AB) nuclei divide and 

 subdivide and some of them are constantly setthng down in parti- 

 cular cells, especially the younger ones, where they form conjugate 



