392 RESEARCHES ON FUNGI 



sterilised by subjecting them in an autoclave to 15 pounds steam 

 pressure for half an hour. One of the blocks was then inoculated 

 with spores taken from a spore-deposit, and a second block was 

 inoculated with a piece of agar containing mycelium taken from one 

 of the Petri- dish cultures already mentioned .^ 



The spores sown on the first of the two blocks soon germinated 

 and produced a mycelium. When the mycelium was very small 

 I examined it in the dark-room, but could not perceive any light 

 comino- from it. However, when it had attained a diameter of 

 about 3 cm. (Fig. 170), I re-examined it one evening when my eyes 

 were well rested and very sensitive. To my surprise I at once 

 perceived that it was distinctly luminous. There was a zone of 

 bright light, about 6 mm. wide, at the periphery of the mycelium 

 where the hyphae had a woolly appearance and were spreading 

 over the substratum, while the central part of the mycelial disc 

 appeared relatively dark and only feebly luminous. In the course 

 of the next six weeks the mycelium completely covered the block 

 of wood and even grew downwards over and into the cotton wool 

 below. The whole block and the cotton wool thus became luminous 

 and I was able to assure myself that, although the peripheral rapidly 

 growing hyphae were giving out the brightest light, yet even the 

 oldest part of the mycelium was giving out a certain amount of light 

 also. In the dark-room I could readily observe the shape of the 

 block, and I could perceive its light at a distance of 10 or even 

 20 feet. The colour of the light appeared to me to be greenish- 

 white like that of the fruit-bodies. A comparison of the mycelium 

 on the wood with the under side of a vigorous fruit-body, made 

 in the dark-room, proved that for equal areas the light emitted 

 from the mycelium is distinctly less intense than that emitted from 

 a fruit-body. I suspect that even the youngest mycelia are lumines- 

 cent and that my failure to detect the phenomenon in very young 

 mycelia was simply due to the feebleness of the hght emitted. 

 Possibly this view might be substantiated by means of photography. 

 The mycelium on the blocks of wood in the cultures continued 

 to give out light for upwards of a year ; and, during this period, it 



1 For undertaking the work of preparing the culture media and making the inocu- 

 lations I am indebted to Miss Irene Mounce. 



