TREMELLA MYCETOPHILA 471 



the excrescences. In other words, I beheve that the supposed 

 parasitic fungus Exobasidium mycetophilum does not exist but that, 

 under certain conditions, Gollybia dryophila develops on its pileus 

 and stipe teratological structures or intumescences which look 

 deceptively like a Tremella. It is on this account that, in the 

 heading of this Section, I have called E. mycetophilum a pseudo- 

 parasite. 



Burt, as we have seen, has expressed the view that the excres- 

 cences are " induced by protracted wet weather during development 

 of the fructification " ; but, with Lloyd,i I am disinclined to accept 

 this explanation. As we know, England has a very damp climate 

 and often experiences protracted wet weather during the develop- 

 ment of Gollybia dryophila fruit-bodies, while the climate in Manitoba 

 is relatively very dry. Yet the excrescences occur in Manitoba but 

 not in England, which is the opposite of what we should expect on 

 Burt's theory. It has yet to be determined whether the excres- 

 cences are inherited from one generation to another or come into 

 existence only as a result of some special, occasionally applied, 

 external stimulus. It may be that there are races of Colly bia 

 dryophila which are especially prone to become malformed. How- 

 ever, although at present we do not know what is the true cause 

 of the origin of the excrescences, their existence reveals to us an 

 unsuspected plasticity in the fruit-body of an agaric which was 

 previously believed to possess a form that could only vary within 

 verv restricted limits. 



A Morchelloid Modification of CoUybia velutipes.— In con- 

 cluding this Chapter, attention may be called to the fact that, in 

 addition to Gollybia dryophila, there is another Gollybia which some- 

 times has abnormal fruit-bodies, namely, G. velutipes. 



A teratological form of Gollybia velutipes was found in France 

 and described by Legue^ in 1909. In this the pileus, although pro- 

 vided with gills, has an alveolate upper surface, reminding one of a 

 little Morchella esculenta (Fig. 195). In a normal pileus (Fig. 202, 

 p. 490 ; also Vol. II, Fig. 15, p. 47) the hymenium, of course, is 



1 C. G. Lloyd, loc. cit., p. 662. 



2 L. Legue, " Note sur une forme anomale de Collyhia velutipes Curt.," Bull. Soc. 

 Myc. France, T. XXV, 1909, pp. 120-122. 



