CRITERIA OF SEX 199 



of a diploid mycelium ; and (6) the aerial hyphae, apart from the 

 oidiophores, excrete relatively few and small drops of hquid along 

 their surface. 



In a diploid myceUum of Coprinus lagopus : (1) the nuclei occur 

 in the hyphae in pairs, and each pair of nuclei divides conjugately ; 

 (2) the septa are provided with clamp-connexions ; (3) the lateral 

 branches of a leading radial hypha come away at a relatively acute 

 angle, 10°-45° ; (4) the mycelium never produces any oidiophores 

 or oidia ; (5) the" aerial mycelium, as viewed with the naked eye, 

 is denser, more protuberant, and more conspicuous than that of 

 a haploid mycelium ; and (6) the aerial hyphae excrete relatively 

 numerous and large drops of liquid at frequent and fairly regular 

 intervals along their surface.^ 



Illustrations of a haploid mycehum of Coprinus lagopus are 

 provided as follows: for the macroscopic appearance. Fig. Ill ; 

 for the wide-angled mode of branching of the leading radial hyphae, 

 for the presence of plain septa and absence of clamp-connexions, 

 and for the formation of hyphal fusions. Fig. 112 ; for oidial fructifi- 

 cations, Figs. 113-116 ; and for solitary nuclei, represented diagram- 

 matically. Figs. 140 and 147, which will be introduced later in a 

 discussion of the diploidisation process (pp. 269 and 279). 



Illustrations of a diploid mycehum of Coprinus lago2ms are pro- 

 vided as follows : for the macroscopic appearance. Fig. 117 ; for 

 the narrow-angled mode of branching of the leading radial hyphae, 



1 Richard Harder (" Zur Frage nacb der Rolle von Kern und Protoplasma im 

 Zellgeschehen und bei der tjbertragung von Eigenschaften," Zeiischriftfiir Botanik, 

 Bd. XIX, 1927, pp. 350-351) observed that in Pholioia mulahilis, the rate of growth 

 of a diploid mycelium is about twice as great as that of either of the two haploid 

 m3'celia from which it has been derived. By micro-dissection of hj^hae he succeeded 

 in obtaining from diploid mycelia uninucleate cells which grew into haploid mycelia. 

 These artificially produced haploid mycelia had a rate of growth of only about 

 half that of the diploid mycelia from which they had come. In Coprinus lagopus, 

 in the course of my experiments, I have often noticed that a haploid mycelium, 

 on becoming diploidised, increases slightly its rate of growth (vide Figs. 128 and 129). 

 If exact comparative measurements of the rate of growth of a diploid mycelium cf 

 C. lagopus and of the two haploids from which it has been derived were to be made, 

 it would probably be found that the diploid always grows slightly more rapidly than 

 either of the haploids. Possibly it is a general rule in the Hymenomycetes that 

 diploid mycelia grow faster than their component haploids ; but whether this is so 

 or not needs to be decided by exact investigation. 



