440 



RESEARCHES ON FUNGI 



where Omphalia flavida flourishes, I have not been able to go into 

 Coffee plantations, pluck spotted leaves, examine them in the dark, 

 and observe their luminescence ; but Professor Albert Miiller of 

 the Mayagiiez College, Porto Rico, has recently done this,^ thus 

 proving beyond doubt that, so far as the emission of light is con- 

 cerned, the spots on Coffee leaves in the open resemble the spots 

 on leaves of Bryophyllum, Oleander, etc., in the laboratory at 

 Winnipeg. 



In the spring of 1928 and also on September 3 and December 4 

 of the same year. Professor Miiller made field observations on the 

 luminosity of infected leaves in a Coffee plantation in Porto Rico, 

 and he described his observations to me in two letters, from one 

 of which the following has been extracted. " My experience A\ith 

 Omphalia flavida has been very interesting. I saw luminosity for 

 the first time when I entered my darkened laboratory and picked 

 up a moist chamber containing leaves bearing the typical spots of 

 the disease. This led to field expeditions for observing the pheno- 

 menon in the open. It was found necessary to select nights when 

 the moon was absent and situations where the brightness of the 

 tropical stars did not interfere. Another factor of the environment 

 played a part in the form of fire-flies, large numbers of which flit 

 about the Coffee trees or rest upon the leaves, giving off a very 

 bright light. After the fire-fiies had been dispersed, it was easy to 

 observe luminosity in the numerous spots on the leaves. This 

 luminosity was quite faint compared with the luminosity of a fire-fl}' 

 placed on a leaf near the spot, yet quite bright compared with the 

 himinosity of entire dead leaves of the CJuava shade- trees found 

 lying on the ground underneath, giving off a dull glow. An attempt 

 was made to ascertain from what distances the luminosity of Coffee 

 leaf-spots could be seen. From two to three feet the spots showed 

 brightest. From six to ten feet one could state positively that 

 luminosity was visible, but beyond ten feet imagination seemed to 

 influence the decision of the observer." 



It is possible that the luminosity of Omphalia flavida leaf-spots 

 was actually observed by those engaged in coffee-growing half a 

 century ago ; for, in 1880, Mr. C. Michelsen, the Commissioner of 



1 In lift., 1928. 



