BIOLUMINESCENCE IN ARMILLARIA MELLEA 429 



luminous leaves in the manner just described is reproduced in 

 Fig. 181. The design was drawn with Indian ink on a sheet of clear 

 glass and, when this was placed in the printing-frame, the dried 

 ink was in contact with the sensitive film of the photographic 

 plate. As before, the negative was exposed to the light emitted 

 by the leaves for a period of 50 hours. 



Remarks on the Bioluminescence of Armillaria mellea. — In the 

 forests of Europe and North America Armillaria mellea (Fig. 38, 

 p. 87 ; also Vol. II, Fig. 73, p. 203) is an exceedingly common 

 fungus ; and there can be no doubt that, in these regions, its 

 mycelium is the chief cause of the production of luminous wood. 

 For some general remarks on A. mellea, including observations on 

 some luminous wood found on the shore of Lake Winnipeg, the 

 reader is referred to Chapter IV. ^ 



It is a striking fact that in Armillaria mellea, while the 

 mycelium invading the cells of the organic substratum and the 

 rhizomorphs are luminescent, the fruit-body is perfectly dark. This 

 restriction of the property of luminescence to the vegetative parts 

 of A. mellea, so often noticed by field mycologists, also holds true 

 under laboratory conditions. Thus Molisch,^ who beginning with 

 spores raised the sporophores of A. mellea in pure cultures, says : 

 "It is remarkable that the fruit-body (Hut) of the Honey Fungus 

 (Hallimasch), which nevertheless springs from the dark-coloured 

 mycelial cords of the rhizomorpha, gives out no light at all." 



It is true that, as a rule, the fruit-body of A. mellea emits no 

 light whatever from either its outer or inner tissues. Yet, on one 

 occasion, in certain fruit-bodies collected in Canada, I observed 

 that a perceptible amount of light was given out by the interior 

 hjrphae of the lower part of the stipe. The conditions under which 

 this unexpected observation was made will now b^ recorded. 



On October 14, 1921, at Kenora, central Canada, I gathered 

 some fresh fruit-bodies from a stump, took them to a dark room at 

 mid-day, and carefully examined them for luminescence ; but they 

 did not give out the faintest appreciable amount of light. I there- 

 upon split a few of them down the middle, wrapped them up in 

 moist newspaper, and left them until 7 p.m. At that time, a walk 

 ^ Pp. 86-89. 2 Hans Molisch, Leuchtende Pflanzen, Jena, 1904, p. 28. 



