PANUS STYPTICUS LUMINESCENS 403 



block, immersed the test-tube at once in the ice-water of tlie second 

 beaker, and then immediately brought this second beaker with its 

 contents to me in the dark-room. Thereupon, I brought the test- 

 tube up to the side of the beaker and observed that the fruit-bodies 

 were still luminescent, although faintly. Miss Mounce also soon 

 perceived the light emitted. Shortly after this I took the beaker 

 into the laboratory and observed that the thermometer in the test- 

 tube still registered 0° C. This experiment, which was repeated 

 with variations with other fruit-bodies, clearly proves that the fruit- 

 bodies of Panus stypt. luminescens are still faintly luminous at 0° C. 



— 3-5° to — 5° C. To observe the effect of temperatures less 

 than 0° C. on luminescence, I exposed some fruit-bodies in the open 

 air at Winnipeg on suitable evenings in December. 



Six fruit-bodies, which at the laboratory temperature of about 

 22° C. were strongly luminous, were placed with gills uppermost 

 in the middle of a large crystallising dish. This dish was then put 

 into a much larger lidless cardboard box lined with black paper, 

 and the whole was then set outside on a flat roof, so that the fruit- 

 bodies were exposed freely to the open sky. The temperature of 

 the air was recorded by means of two thermometers placed in the 

 dish. After the fruit-bodies had been exposed, I made observations 

 for temperature and luminescence as follows. I lifted up the ther- 

 mometers and read them in the open in a weak beam of light coming 

 through a laboratory window. To observe the fruit- bodies for 

 luminescence in complete darkness, I covered my head and the large 

 cardboard box for a few seconds with a black cloth. To keep my 

 eyes in a sensitive condition I paced about the roof or otherwise 

 avoided artificial light as much as possible. 



Observations were begun at 6-37 p.m. on December 7, 1921, and 

 were continued for 2-5 hours. During this period the temperature 

 of the air slowly decHned from — 3-5° to — 4- 1° C. after one hour, 

 and to— 5°C. after 2-5 hours. The fruit-bodies glowed brightly 

 for the first half hour, feebly at the end of an hour, and not at 

 all at the end of 2-5 hours. The data for time, temperature, and 

 luminescence are embodied in the Table on p. 404. 



At the end of the exjieriment (after 2-5 hours), I covered the 

 dish containing the fruit-bodies with a glass lid which had been 



