266 RESEARCHES ON FUNGI 



black owing to spores being developed all over its gills ; (3) its 

 pileus always expands fully ; (4) it liberates a great many spores ; 

 and (5) its spores, sexually, are of all the four possible kinds : (AB), 

 (ab), (Ab), and [aB).^ 



The relative earliness of fruiting in diploid mycelia of Coprinus 

 lagopus as compared with haploid mycelia is illustrated in Fig. 139. 

 The fourteen cultures (pairings of haploid mycelia) there shown 

 were started on the same day. The nine which became diploidised 

 have all produced fruit-bodies, while the five which remained 

 haploid either have not yet begun to form fruit-bodies or their 

 fruit-bodies are relatively less advanced than those in the diploid 

 cultures. 



There can be no doubt that, from the point of view of repro- 

 ducing the species, it is advantageous for Coprinus lagopus to 

 produce diploid fruit-bodies rather than hajDloid fruit-bodies. This 

 being so, and since diploid fruit-bodies are produced only on diploid 

 mycelia and haploid fruit-bodies only on haploid mycelia, it is far 

 better for C. lagopus to develop its fruit-bodies on diploid mycelia 

 than on haploid mycelia. 



Since, in Coprinus lagopus, diploid mycelia produce much more 

 effective fruit-bodies than haploid mycelia, it is important that the 

 mycelium of the fungus present in a dung-ball should become 

 diploidised to the greatest possible extent and particularly at the 

 surface of the dung-ball where the fruit-body rudiments come into 

 existence. 



One of the means employed by Coprinus lagopus for increasing 

 the amount of diploid mycelium in a dung-ball which has received 

 many spores is the diploidisation of haploid mycelia by appropriate 

 diploid mycelia, i.e. the diploidisation of {AB) and {ab) mycelia by 

 {AB)^{ab) mycelia and the diploidisation of (^6) and {aB) mycelia 

 by {Ab)-\^{aB) mycelia. 



As an illustration of the advantage accruing to Coprinus lagopus 



^ Presumably, in Coprinus lagopus, as in other Agaricineae, in a haploid fruit- 

 body the cells contain isolated non-conjugate nuclei and each young basidium a 

 single nucleus, while in a diploid fruit-body the cells contain conjugate nuclei and 

 each young basidium a pair of conjugate nuclei which soon fuse together to form 

 a fusion nucleus which undergoes reduction ; but I have not verified these 

 suppositions by means of cytological observations. 



