PANUS STYPTICUS LUMINESCENS 387 



declines, finally becoming invisible shortly before the end of the spore- 

 discharge period. The longest period of luminescence for any one 

 fruit-body, severed from its substratum and kept on wet cotton wool 

 in the laboratory, was about ten days. 



A fruit-body takes about 10 days to develop from a tiny rudiment 

 to full size and is luminescent from its first appearance on the 

 surface of the wood. Since mature fruit-bodies when taken into 

 the laboratory may give out light for 7 to 10 days, doubtless under 

 natural conditions the duration of the bioluminescent period is at 

 least three or four weeks. Some fruit-bodies which developed on a 

 block of wood in the laboratory gave out light for about a month ; 

 and one such fruit-body, which grew under deficient moisture 

 conditions, was actually luminescent for three months.^ 



In the hope of extracting the photogen I placed a highly lumines- 

 cent fruit-body between two glass plates and pressed the plates 

 tightly together with my fingers. Within a minute the fruit-body 

 had been completely flattened, its sap expressed, and its cells 

 broken up. As the crushing process began, the light began to fade, 

 and when it was completed, the light was no longer emitted. The 

 sap extracted, therefore, was non-luminous. 



A dried fruit-body was taken and broken into powder with the 

 help of a pestle and mortar. The powder was then taken into the 

 dark-room and moistened with water. The mixture of powder and 

 water never emitted any light at all. 



The two experiments just described indicate that it is not 

 possible to extract a photogen from Panus stypt. luminescens by 

 mechanically squeezing out its sap. This is in accord with the 

 experience of other workers on luminescent fungi. As already 

 mentioned,'-^ Kawamura failed in an attempt to extract a photogen 

 from Pleurotus japonicus and Ewart failed in a similar attempt 

 with Pleurotus caiidescens. 



The difficulty in extracting a photogen from fungi is doubtless 

 due in part to the fact that the photogen in these plants is not present 

 as an extracellular secretion or excretion, as it is in some animals 

 such as Pholas, but is formed intracellularly.^ When the hyphae 



1 Vide infra, p. 395. ^ Vide supra, p. 382. 



3 Cf. H. Molisch, loc. ciL, p. 118. 



