PANUS STYPTICUS LUMINESCENS 385 



The fruit-bodies used for my observations were usually removed 

 from the woody substratum upon which they grew, and wet cotton 

 wool was applied to their upper surfaces for an hour or two until 

 they had absorbed all the water that they could take in. They 

 were then placed, gills downward, on wet cotton wool covering the 

 base of a large crystallising dish, and the dish was closed with a 

 glass plate. Under these conditions many of the fruit-bodies 

 continued to glow for 7-10 days. The examination of the fruit- 

 bodies for luminescence took place in a photographic dark-room 

 kept at a temperature of about 18°-22'^ C. 



To observe the light given out by a fruit-body it is necessary 

 that one's eyes should be in the proper physiological condition. 

 I found that, if I went into the dark-room at mid-day after my eyes 

 had been acted upon by bright daylight, I was often obliged to wait 

 5 minutes or even longer before I could see any glow at all, even 

 from the brightest fruit-bodies. Subjection to darkness enormously 

 increases the sensitiveness of the eyes ; and, after I had spent 

 10 to 15 minutes in the dark-room, the fruit-bodies usually appeared 

 to glow with their maximum intensity. Experience, supported by a 

 series of exact experiments already recorded,^ has taught me that 

 my eyes are much more sensitive to feeble light in the evenings 

 after sunset than at mid-day. After an hour's walk in the evening 

 in the dark, or after sleep, I found that I could see the light of 

 the fungi immediately I entered the dark-room, and could even 

 perceive it distinctly outside the room in weak diffuse daylight. 

 That Dr. Bisby, one evening when walking in a wood, discovered 

 a group of the fruit-bodies by the light they gave out has already 

 been mentioned.^ At the time, his eyes must have been in a highly 

 sensitive condition. In studying the luminescence of fungi, there 

 can be no doubt that the physiological condition of the eyes is a 

 factor of considerable importance. 



In full-grown fruit-bodies the under surface of the pileus is 

 strongly luminous, the upper side faintly luminous, and the stipe 

 not luminous at all. The gills are principally responsible for the 

 emission of the light, but there is a certain amount of radiation 

 emitted also by the pileus-flesh. From a luminous fruit-body 

 1 Vide supra, pp. 373-376. ^ Vide supra, p. 376. 



VOL. III. " ^ 



