220 RESEARCHES ON FUNGI 



attacks of slugs finds its analogy in the fact that 'meadow grasses 

 in general are unprotected against the attacks of horses and 

 cattle. In both instances the individual plants are so numerous 

 that the partial destruction of some, or even many, of them 

 has not been a cause sufficient in the course of evolution to bring 

 about the development of protection by mechanical or other means. 

 A change in the consistence of our terrestrial agarics from soft- 

 fleshy to a degree of mechanical hardness or toughness which 

 would be protective against slugs would, of necessity, be accom- 

 panied by a larger expenditure of fungus material and energy, by 

 a slower rate of development, and by a smaller output of spores 

 per unit mass of mycelium. Thus the protection of fleshy fungi 

 by mechanical means might be purchased at too great a price. 



Absence of Slugs from a Wood in Central Canada. Slugs, 

 which are common in England and in the extreme west of Canada 

 (British Columbia), where the climate is damp and moderately 

 warm, are rare in central Canada, where the climate is very dry 

 and relatively cold. Most native-born Manitobans, so far as I can 

 find out by enquiry, have never seen a Living slug ; and there can 

 be no doubt that the big species of Limax, Arion, etc., which 

 abound in gardens and w r oods in England, are entirely absent from 

 central Canada. 



In the late autumn of 1920, I spent several days at Kenora on 

 the Lake of the Woods, central Canada, studying the fleshy fungi 

 in the woods ; and, although I made a careful search, I could not 

 find a single agaric damaged by a slug. 



In the autumn of 1921, I was again at Kenora, and again noted 

 the freedom of the fleshy agarics from slug damage. However, on 

 this occasion, under a rotten log in a wood not far from dwellings, 

 to my surprise, I came upon two small slugs. These were dark 

 brown or blackish and about half an inch long, and they had evi- 

 dently been feeding upon the delicate pilei of some Trogia crispa 

 fruit-bodies which were attached to the log in their immediate 

 vicinity. They appeared to belong to the genus Agriolimax and 

 may have been A. campestris. 



According to Frank C. Baker, 1 Agriolimax campestris and 



1 In Hit. 



