EXPLANATION OF PLATES 309 



Fia. 3. — A hyphal fusion between the two hyphae which were in contact has 

 just taken place by dissolution of the two appressed cell-walls, and already the 

 (AB) nucleus of the diploid half of the compoimd cell is dividing and forming two 

 daughter nuclei. 



Fia. 4. — The division of the (AB) nucleus has been completed, and one of the 

 daughter (AB) nuclei has moved into the {ab) half of the compound cell and has 

 become associated with the (ab) nucleus there present. Thus a pair of conjugate 

 nuclei has been established in one of the cells of the haploid mycelium {ab), which 

 cell may be said to have become diploidised. 



Fig. 5. — The (AB) nucleus of the newly established conjugate pair is now 

 dividing and one of the daughter (AB) nuclei is destined to pass into a neighbouring 

 (ab) cell. 



Fig. 6. — One of the daughter {AB) nuclei of Fig. 5 has now passed into a 

 neighbouring {ab) cell and has thus diploidised it. The passage from one cell to 

 the other was made possible by the breaking down of the septum between them, 

 but such a breaking-down of the septum has not been represented in the diagram. 

 A septum cutting off the diploid mycelium {AB)-\-{ab) from the original haploid 

 mycelium {ab) is now shown. 



Fig. 7. — The two {AB) nuclei in the recently diploidised cells of the haploid 

 mycelium are now dividing. 



Fig. 8. — Two of the daughter {AB) nuclei shown in process of formation in 

 Fig. 7 have now moved into neighbouring cells and have thus diploidised them. 

 One of these cells (on the right) is a terminal one, and already the pair of conjugate 

 nuclei there established is about to divide, for a hook for the reception of one of 

 the nuclei has been formed. 



Fig. 9. — In the main hypha of the originally haploid mycelium {ab) two more 

 divisions of {AB) nuclei are now in progress ; while, in the end cell of the hypha on 

 the right, conjugate division of the pair of conjugate nuclei is well advanced. 



Fig. 10. — The main hypha of the originally haploid mycelium {ab) and its two 

 branches have become completely diploidised, and conjugate division of the pairs 

 of nuclei in its end cells, accompanied by the formation of a clamp-connexion, is 

 taking place or is about to take place. A separate {ab) hypha on the right is still 

 in the haploid condition, but a branch of it is growing toward the central already- 

 diploidised hypha and is about to fuse with it. When this hyphal fusion has been 

 established, the now separate haploid hypha {ab) will soon become diploidised. 



Fig. 11. — The central diploidised hypha and one of its branches have each 

 formed an additional clamp-connexion. The union of a branch of the still haploid 

 hypha {ab) on the right with the central diploidised hypha has now taken place. 

 An {AB) nucleus is dividing in the connecting hypha. One of the daughter {AB) 

 nuclei will pass into the {ab) hypha and there begin the diploidisation of its cells. 



Fig. 12. — The whole of the originally haploid mycelium {ab) has now become 

 diploidised except a short hypha (below) of which three cells have been shown ; 

 but a very short branch of the diploidised central hypha is seen growing toward it 

 in the extreme lower right-hand corner of the diagram. This very short branch 

 will meet and fuse with the short {ab) hypha ; and, after the fusion has taken place, 

 the cells of the short {ab) hypha will soon become diploidised. 



