BIOLUMINESCENCE IN FUNGI 371 



having been confused with the fruit-bodies of P. ostreatus, they have 

 been the cause of numerous cases of poisoning, resulting in many 

 deaths. The light is emitted by the gills only. The hymenium, 

 subhymenium, and trama are all luminous, but no light is emitted 

 by the spores. A fruit-body with a luminous area of 100 square cm. 

 gives sufficient light in the dark to enable one to see Roman 

 letters about 8 mm. wide, and the light can be well perceived at a 

 distance of at least 30 metres. The light is white, not greenish, 

 bluish, or yellowish, as in most fungi. Photographic images of the 

 luminous surface of a fruit-body, taken in a dark room with an 

 exposure of 7-5 or even 24 hours, were all very faint ; but, when 

 leaves were placed between the under side of a pileus and a very 

 sensitive photographic dry-plate,^ with an exposure of nearly two 

 hours, some excellent dark prints on a white background (Fig. 164) 

 were secured. The minimum temperature for the emission of light 

 is 3°-5° C, the maximum 40° C, and the optimum about 10°-15° C. 

 When the fruit-body is suddenly immersed in nitrogen gas, the 

 luminescence begins to fade after 10 seconds, becomes very feeble 

 after 50 seconds, is scarcely recognisable after 1 minute 20 seconds, 

 and finally becomes completely invisible after 1 minute and 

 40 seconds. When a fruit-body is plunged into hydrogen gas, the 

 luminescence begins to fade after 10 seconds and becomes invisible 

 after 30 seconds.^ Chloroform vapour causes the light to vanish 

 in 55 seconds and ether vapour in 1 minute 50 seconds. If, after 

 being immersed in ether vapour for 1 minute 50 seconds, the fruit- 

 body is placed in pure air, the luminescence returns after 30 seconds- 

 Exposure of a fruit-body to oxygen gas causes no change in the 

 intensity of the light. In oxygen, therefore, the fungus behaves 

 just as it does in air. 



In England there are no Agaricineae in which the pileus is 

 luminous, but in Canada and the United States there are two : 

 Panus sfypticus luminescens and Clitocybe illudens. 



Clitocybe illudens, in North America, is popularly known as Jack- 



1 " Ilford Alliance, fastest." 



2 Kawamura told me in a personal interview that " thirty minutes " in his text 

 was a misprint for " thirty seconds." In citing his results I have therefore intro- 

 duced the correction. 



