FALCK'S THEORY 221 



any two would become slightly warmed, and that, in consequence, 

 useful convection currents would be formed. However, since the 

 fruit-bodies are developed at some height on trees (c/. Fig. 1), any 

 such convection currents would most probably always be swamped 

 by more pronounced air-movements. If it be granted that there 

 is no special adaptation for producing heat in the fruit-bodies of 

 Polyi')orus squamosus, then the adaptation part of Falck's theory 

 becomes much weakened, for it was with this species that one of 

 the highest rises in temperature was obtained in the insulation 

 experiments. 



The maggots which so frequently are to be found in fruit-bodies, 

 in most instances at least, seem to me to be in no way beneficent 

 to the latter, and, in general, I am strongly inclined to look upon 

 them simply as harmful parasites. It would need a special investi- 

 gation to decide the matter, but it seems probable that of two 

 fruit-bodies equal in size, but one of them free from maggots and 

 the other badly infected, the former would produce and liberate the 

 greater number of spores. Even if they both liberated the same 

 number, we could still regard the maggots in the same light as some 

 gall-insects, i.e. as parasites which, as a rule, do no very appreciable 

 amount of harm, and for getting rid of which the plants concerned 

 possess no mechanism. Sometimes the harm done is quite obvious. 

 In a number of instances in the field, I have noticed fruit-bodies of 

 Amanita ruhescens, &c., with the gills perforated and otherwise 

 damaged by maggots long before the spores had all been shed. 

 Occasionally, at an equally early period, the flesh of a pileus becomes 

 so weakened by the inroads of these animals that it can no longer 

 support the gills in the requisite vertical planes. 



Doubtless, the heat which an expanding, maggot-free pileus 

 produces, like that arising in the rapidly opening capitula of Com- 

 positai, is due to respiration accompanying other active metabolic 

 changes. The gills in particular, whilst developing and setting free 

 their millions of spores, have a large amount of work to do. There 

 seems no reason to suppose that the fruit-bodies give rise to any more 

 heat than is necessitated by the processes concerned in rapid growth. 

 Probably putf-balls, which certainly do not use any heat which they 

 develop for scattering their spores, would become warmed on insula- 



