COPRINUS STERQUILINUS 



155 



into a diploid one spontaneously in a homothallic species, and after 

 union with another myceUum containing complementary sexual 

 factors in a heterothalUc species. A diploid mycelium is character- 

 ised by having its nuclei r\ r\ r\ r\ r\ 



'to 



n 





.4- 



in pairs, by the pairs of 

 nuclei dividing conju- 

 gately, and by the forma- 

 tion of a clamp-connexion 

 at each septum. The 

 stages in the formation of 

 a clamp-connexion in a 

 diploid mycelium, as repre- 

 sented by Mile Bensaude, 

 are shown in Fig. 85. fig. 



Social Organisation in 

 Coprinus sterquilinus. — 

 To illustrate the phenome- 

 non of social organisation 

 in the Hymenomycetes it 

 will be convenient to con- 

 sider the mode of growth 

 and reproduction in Co- 

 prinus sterquilinus. This 

 fungus has already been 

 treated of from other 

 points of view in Volume 

 III 1 and in the three pre- 

 ceding chapters of this 

 Volume IV. Its mycelium 

 is homothallic and grows 

 on horse dung, while its 

 fruit-bodies are of large 

 size. A single average fruit-body is so large that, during its de- 

 velopment and expansion, it drains and exhausts a large mass of 

 mycelium. In the production of a large fruit-body (Fig. 8(5), the 

 mycelium used up may be that present either in two or more small 

 1 These Researches, vol. iii, 1924, pp. 177-259. 



85. — Diagram sliowing, from left to right, a 

 conjugate nuclear division and the formation of 

 a clamp-connexion in a hypha of a diploid my- 

 celium of Coj^rinus lagopus ( = C . fimetarius of 

 Mile Bensaude). The (-1-) sign indicates a 

 nucleus of one sex, and the ( — ) sign a nucleus 

 of opposite sex. The ( + ) nucleus and the ( — ) 

 nucleus have been derived respectively from 

 a ( -1- ) nucleus and a ( — ) nucleus whicli became 

 associated with one another when a ( -f ) my- 

 celium and a ( — ) mycelium fused with one 

 another and diploi ised one another. In stage 

 no. 1, a hook is growing backwards ; in stage 

 no. 2 the ( -f ) nucleus has passed into the hook 

 and the ( — ) nucleus is by the side of it in the 

 main hypha ; in stage no. 3, the ( + ) and the 

 ( — ) nuclei are dividing conjugately ; in stage 

 no. 4, two .septa are being formed one across 

 the main hypha and one across the top of the 

 hook, and for the moment the ( + ) nucleus is 

 a prisoner in tlie hook-cell ; in stage no. 5, the 

 lower end of the liook has fused with the main 

 hypha and the ( + ) nucleus is passhig down- 

 wards toward its fellow ( — ) nucleus. Each 

 of the two new cells now contains a pair of 

 conjugate nuclei and the clamp-connexion has 

 been completely formed. Copied by Dr. Nellie 

 Carter from Mile Bensaude's Eccherches sur le 

 cycle evolutif et la sexualite chez les Basidio- 

 mycetes (Nemours, 1918). 



