174 RESEARCHES ON FUNGI 



immersed in the liquid (c/. Fig. 98). Under these aquatic con- 

 ditions no spores were formed. However, a hypha of one of 

 the united monoconidial myceUa, which happened to be at the 

 edge of the drop, managed to push its way out of the liquid and to 

 grow into the air. The aerial hypha grew in length and branched 

 and rebranched so as to form a large conidiophore, and soon at 

 the end of each branch it produced a httle ball of green conidia. 

 With the microscope I was able to observe that, during the forma- 

 tion of the conidiophore and its spores, the compound mycelium 

 gradually became exhausted of its contents, so that at last the 

 hyphae seemed to be empty. There can be no doubt that the 

 compound myceUum, in supplying food materials to the conidio- 

 phore, acted as a unit, and that every one of the monoconidial 

 mycelia of which it was made up contributed something to the 

 formation of the spores. Of the hundreds of mycelia which were 

 formed by the germination of the conidia soon after the culture 

 was started, only one succeeded in carrying out the process of repro- 

 duction, and it developed its conidia to some extent by drawing 

 upon its own contents, but chiefly at the expense of the contents 

 of all the other mycelia which remained sterile. The co-operation 

 of the individual mycelia with one another led to the production 

 of far more spores than could have been produced by competition. 

 The reproductively successful mycelium owed its success to its 

 position in the medium : it happened to be near the edge of the 

 drop and therefore had the good fortune to push one of its hyphae 

 beyond the edge of the drop into the air, whereas all the other 

 mycelia happened to be farther within the drop and to remain 

 totally immersed in the watery fluid where, owing to the inhibitory 

 action of the water, the production of conidia was impossible. The 

 parallel between the social organisation which has just been described 

 for Trichoderma lignorum and that previously described for Coprinus 

 sterquilinus is very striking. In both the Mould and the Hymeno 

 mycete most of the co-operating individual myceUa remain sterile, 

 while only one or a very few of them succeed in producing spores, 

 but the species benefits in that the spores are produced with greater 

 certainty and in greater numbers. 



Further observations on social organisation in Trichoderma 



