384 RESEARCHES ON FUNGI 



the mycelium of Armillaria mellea growing within a rotten log or 

 in the stump of a tree. I fail to see any biological advantage in 

 the emission of light from the fruit-bodies of luminous species of 

 Pleurotus and Panus. Ewart/ in writing about Pleurotus candescens, 

 says : " As to the biological significance of the luminosity, its re- 

 striction to the gills shows that its present function is evidently to 

 attract molluscs, as well as creeping and flying insects, which may 

 aid in the distribution of the spores." With this view I cannot agree. 

 There is no evidence that the light emitted by the fungus does 

 attract the animals mentioned. The light would be useless for such 

 a purpose during the day. Slugs have very weak eyes and a very 

 strong olfactory sense. As I have shown in Volume II, they find 

 distant fungi chemotactically.^ It is not certain that they could 

 perceive a luminous fungus in the dark unless they were very near 

 to it, and it is very doubtful whether they would crawl towards an 

 object, at night in the open, merely because it emitted light. The 

 phototaxis hypothesis therefore seems to me to be highly improbable. 

 I am rather of the opinion that the emission of light by fungus 

 fruit-bodies is of no biological advantage whatever, but takes place 

 merely as an accompaniment of some chemical reaction necessitated 

 hj metabolism. 



Further Observations on the Bioluminescence of Panus styp- 

 ticus luminescens. — Stimulated by reading Kawamura's paper on 

 Pleurotus japo7iicus published in 1915 and Harvey's book entitled 

 The Nature of Animal Light published hi 1920, I reinvestigated the 

 bioluminescence of Panus stypt. luminescens in the autumn of 1921. 

 The results of this second investigation will now be communicated. 



Panus stypt. luminescens occurs but very rarely in central Canada. 

 It was therefore necessary for me to procure fruit-bodies from other 

 parts of North America. Material was kindly supplied to me from 

 Toronto by Professor J. H. Faull, from Ann Arbor, Michigan, by 

 Professor C. H. Kauffman, and from Minneapohs by Professor 

 E. C. Stakman. It was sent in the dry condition and, after arrival, 

 it was revived as required by moistening it. The younger fruit- 

 bodies in all the collections proved to be luminescent. 



1 A. J. Ewart, loc. cit., p. 174. 



2 These Researches, vol. ii, 1922, pp. 222-235. 



