84 RESEARCHES ON FUNGI 



produced. The failure of C. sterquilinus to develop in the three 

 experiments upon unsteriHsed horse dung described above cannot 

 be attributed to any want of vitality of the spores. It seems rather 

 to have been due to the fact that the fungus was obliged to compete 

 with other fungi under disadvantageous conditions and was beaten 

 in the struggle. Upon grass settle the spores of many coprophilous 

 fungi, and grass and spores pass down the alimentary canal of the 

 horse together. Probably the initial steps in the germination of 

 the spores are taken in the faeces just before these are extruded. 

 We may therefore suppose that, as soon as dung-balls are deposited 

 on the ground, innumerable spores within the balls begin to form 

 mycelia. Now it is evident that spores of a coprophilous fungus 

 which settled from the air on the surface of a fresh horse-dung ball 

 would have but a poor chance of producing mycelia that could 

 successfully compete with the mycelia produced from spores which 

 had passed down the ahmentary canal and were scattered through 

 the substance of the dung-mass. Under the most favourable 

 conditions of culture and temperature (30° C), in a long series of 

 experiments, it was found that the spores of C. sterquilinus do not 

 begin to show signs of germination until 12-24 hours have passed, 

 although within two days between 80 and 90 per cent, of the total 

 number of spores produce germ- tubes. It is clear therefore that, 

 in Experiments I, II, and III described above, the spores of 

 C. sterquilinus could produce mycelia only long after their deposi- 

 tion, at a time when, as there is every reason to believe, the spores 

 of other fungi, including Coprini, had already developed an 

 abundance of mycelium which was penetrating the dung-mass in 

 all directions and using up rapidly the most available and the most 

 nutritious food-stuffs. Under these conditions, Coprinus ephemerus 

 and C. lagopus, together with other fungi, owing to priority of develop- 

 ment, seem to have actually suppressed any competition from 

 Coprinus sterquilinus. 



The experiments and observations recorded above seem to 

 warrant the conclusion that the successful spores of Coprinus 

 sterquilinus under natural conditions are those which are swallowed 

 by horses and taken down their alimentary canals, and that any- 

 spores which are not so swallowed, even should they settle on 



