STUDIES ON THE LUMINOUS FUNGUS. 21 



(g) To see what would happen by exhausting the air, the 

 fungus was placed, luminous surface upward, in the bell-glass of 

 air exhauster. Pumping the air out for one minute, when the 

 atomospheric pressure within registered 0.17, the fungus-light began 

 to weaken. As the pressure stood at 0-05 atmospheric pressure, 

 the light was very weak, but still visible. As the exhausting 

 could not be carried on any further, the air was let in, on which 

 the dimly luminous fungus gradually resumed the original bright- 

 ness. 



(h) In oxygen the fungus -light showed no change whatever, 

 but behaved exactly as in the air. 



VII. Character of the Luminosity. 



The manner in which the present fungus emits light seems 

 to be much the same as that of other fungi and bacteria which 

 are endowed with that power. The light is not intermittent, but 

 maintains an almost steady continuance for a long time. As the 

 fungus becomes decrepit, the light gradually weakens until it 

 finally becomes invisible to the eye. Eainy weather shortens the 

 period of luminosity by causing early decay of the fungus. Lumi- 

 nosity is strongest in fresh specimens in which the gills present 

 a pure white color. It is distinctly much weaker in older speci- 

 mens with gills which have turned somewhat yellowish in color 

 and have begun to bear juicy exudation on the surface.' Usually, 

 the light becomes totally invisible to the eye three days after the 

 setting in of the first sign of fading. Should the fungus rapidly 

 become putrid, it retains a feeble light for a considerable time 

 and that even after it has begun to give off offensive smell. The 

 luminosity is always uniformly spread over the surface of gills ; it 

 never appears spotted or spotwise, unless the tissue is injured. 



