436 RESEARCHES ON FUNGI 



it was kept in the box in the dark. This culture grew well but did 

 not produce any gemmifers in the dark in the course of several 

 weeks. 



Small pieces of agar bearing mycelium were taken from the Porto 

 Rican culture and were used to inoculate the centres of three malt- 

 agar Petri dishes on June 7, 1928. Two of these dishes were then 

 exposed to daylight on a table, whilst the third was exposed to 

 daylight for about one hour and was then enveloped in black paper 

 and placed in a dark cupboard. 



On June 13, i.e. six days after the beginning of the experiment, 

 the condition of the plates was as follows. In the two plates which 

 had been exposed to daylight numerous gemmifers had appeared 

 not only on the mycelium on the pieces of Porto Rican agar used as 

 inoculum but also on the new agar, and on the new agar three 

 distinct concentric zones of gemmifers could be clearly observed. 

 On the other hand, on the plate which had been exposed to light 

 for about an hour and had then been placed in the dark, a certain 

 number of gemmifers had developed on the old mycelium in the 

 inoculum which had been exposed to the light for an hour, whilst 

 no gemmifers whatever had appeared on the new mycelium which 

 had grown out radially in the fresh agar in the dark. At the end 

 of another week, the lighted cultures had developed many zones 

 bearing gemmifers while the darkened culture had developed no 

 such zones, the mycelium of the darkened culture, excepting that 

 in the original inoculum which had been exposed to daylight for 

 about an hour, having remained quite sterile. 



From the above observations we may conclude : (1) that the 

 formation of gemmifers is initiated by the stimulus of light ; and 

 (2) that the mycelium is stimulated to produce gemmifers by an 

 exposure to daylight of one hour or less. 



Ashby 1 observed that both gemmifers and sporophores devel- 

 ojied to maturity in bread cultures in flasks kept in the dark. The 

 production of fruiting structures in this instance may well have been 

 due to the stimulus of light given during the time when the flasks 

 were being inoculated or were being examined from day to day. In 



1 S. F. Ashby, " The Perfect Form of Stilbum flavidum Cke. in Pure Culture," 

 Bulletin of Miscellaneous Information, Royal Botanic Gardens, Kew, 1925, p. 327. 



