228 RESEARCHES ON FUNGI 



as a rule, are produced at some height from the ground. For a 

 slug, the infected trees are often several days' journey apart, and, 

 even if a slug were to travel directly from one to another, spores 

 swallowed on one tree would all be lost in the freces before the 

 next had been reached. From a consideration of the distribution 

 of the fungus and of the movements of slugs it seems impossible 

 that these animals should materially help in spreading the species 

 from tree to tree. A similar argument might be applied to 

 Pleurotus ulmarius and many other species growing on trees, 

 as well as to such fungi as grow on the ground and are characterised 

 by the fruit-bodies developing sporadically at considerable distances 

 from one another. The Russuke, Amanita?, &c, exhibit all the 

 usual arrangements in their fruit-bodies for liberating the spores 

 into the air in such a manner that they may be carried off by the 

 wind. In the absence of slugs, hundreds of millions of spores 

 fall from the gills. We can scarcely suppose that spores thus 

 carried off by the wind have no chance of reproducing the species. 

 It seems probable, therefore, that the wind, even in the case of 

 the Russulse, is still by far the chief agent in spreading the fungi 

 from place to place. 



The conditions necessary for the germination of the spores of 

 many of the higher fungi in nature are unknown. Voglino's 

 observations suggest that small herbivorous animals provide these 

 conditions much more often than has hitherto been supposed. It 

 was recorded in Chapter V. that a single Mushroom (Psalliota 

 campestris), with a diameter of 8 cm., produced 1,800,000,000 spores. 

 We are justified in supposing that a very large Agaric might 

 produce 4,000,000,000. If these were scattered uniformly in nature 

 there would be sufficient of them to provide one for every square 

 inch in a square mile. This calculation may perhaps serve to 

 indicate how widely dispersed the spores of one of the Hymeno- 

 mycetes may become, and how frequently they must be present 

 on grass, leaves, fruits, &c. Herbivorous birds, toads, slugs, insects, 

 worms, &c, must very frequently devour spores with their food. 

 Perhaps then, whilst in general the wind is the chief agent in 

 dispersing the spores of Hymenomycetes, in some species small herbi- 

 vorous animals provide the conditions for their germination and the 



