242 RESEARCHES ON FUNGI 



p. 215), growing on a layer of dung-agar 2-3 mm. thick contained 



in a 15-cm. Petri dish, was found to have 121 leading radial hyphae 



included within each mm. of its periphery (average of several 



22 

 counts). Thecircumferenceof the mycelium was 60 X — = 188 mm. 



The total number of leading radial hyphae at the periphery of the hap- 

 loid mycelium was therefore 121 X 188 or, in round figures, 22,750. 



When a 6-cm.-wide haploid mycehum (AB) is inoculated at its 

 periphery with a tiny fragment of a haploid mycehum {ab) or of a 

 diploid mycelium {AB)-\-{ab), all its leading radial hyphae are 

 converted into diploid hyphae bearing clamp-connexions. This 

 conversion, as we have seen from the results of experiments already 

 described, takes about three days, and the haploid mycehum, 

 during this time, increases its diameter to about 8-5 cm. Since 

 the mycelium undergoing diploidisation increases its diameter from 

 6 cm. to 8-5 cm. before the process is completed, the number of its 

 leading hyphae which are converted from the haploid to the diploid 

 state lies between 22,750 and 32,300. We may therefore assume 

 that, at the periphery of the large haploid mycelium under con- 

 sideration, the number of leading radial haploid hyphae which 

 receive nuclei from the inoculum is not less than 26,000. 



Let us suppose that only one nucleus has passed into the large 

 haploid mycehum from the inoculum. Then, to produce the 

 26,000 nuclei required to make up the conjugate pairs in the 

 26,000 end-cells of the 26,000 leading hyphae of the large (AB) 

 mycehum, the single (ab) nucleus which entered the (AB) mycelium 

 would need to undergo subdivision until its progeny consisted of 

 at least 26,000 nuclei. If this subdivision were to be in the form 

 of a geometrical progression in which the original (ab) nucleus 

 divided once, its two daughter nuclei once, the resulting four nuclei 

 once, and so forth, a succession of 14-15 divisions would be required 

 to produce the 26,000 {ab) nuclei ; but, doubtless, the actual series 

 of nuclear divisions is never so regular as that suggested. If some 

 nuclei cease to divide during the diploidisation process, then others 

 must divide more often. 



When a large 6-cm.-wide haploid mycelium (AB) is becoming 

 diploidised through the action of an inoculum {ab) or {AB)+{ab), 



