PANUS STYPTICUS LUMINESCENS 405 



From the data given in the Table it will be seen that for 5 hours 

 (observations 2-7) the temperature to which the fruit-bodies were 

 exposed varied from — l°to — 2'7°C. and that during this time 

 the fruit-bodies continued to emit light, although only faintly 

 at — 2-7°C. After midnight the temperature descended from 

 — 2-7°C. and in the morning (observation 8) was — 10° C. 

 At — 10° C. the fruit-bodies were non-luminous. On taking them 

 into the dark-room, as in the previous experiment, their lumines- 

 cence began to re.turn after about 5 minutes and, in less than half 

 an hour after their exposure to the warm air, they appeared to be 

 glowing with their maximum intensity. Extremely low tempera- 

 tures, therefore, do not appear to injure the photogen in any way 

 but only to retard its action. 



The two foregoing experiments, together with others which 

 I shall not describe, point to the conclusion that in Partus 

 stypt. luminescens the minimum temperature for luminescence lies 

 between - 2° and - 5° C.i 



It may be that the fruit-bodies of Panus stypt. luminescens are 

 luminescent until their cell-sap freezes, but this possibility was not 

 investigated. 



38° C. Some luminous fruit-bodies were placed in a test-tube 

 containing a thermometer (c/. a in Fig. 173, p. 402) and the test- 

 tube was plunged into water at 38° C. contained in a large beaker 

 which was insulated with cotton wool. The beaker contained a 

 thermometer and a looped stirring rod. The apparatus was set in 

 the dark-room. In the dark, by looking through the wall of the 

 beaker, the water in the beaker, and the wall of the test-tube, I was 

 able to observe the fruit-bodies and to watch the changes in their 

 luminosity. The temperature of the water was kept sufficiently 

 constant by adding hot water to the beaker when necessary. As 



^ There are organisms which give out light at still lower temperatures, e.g. the 

 Beetle Lampyris at — 10° C. (Macaire, 1921), and certain Bacteria : Pseudomonas 

 javanica at — 20° C. (Eijkman, 1892) ; Bacterium phosphorescens at — 12° C. 

 (Lehmann, 1889): light bacteria, at — 11 -5° C. (Harvey, 1913); and light bacteria 

 at — 7° C. (Tarchanoff, 1902), The power to luminesce, in some organisms at least, 

 is not destroyed by exposure to liquid air; for, on raising the temperature, light 

 again appears (Macfayden, 1902). Vide E. N. Harvey, The Nature of Animal 

 Light, 1920, pp. 157, 159. 



