THE EFFECT OF SUNLIGHT UPON SPORES 25 



exposed to the sun. During their transportation by the wind, 

 spores must often be exposed to sunlight for several hours together ; 

 by analogy, therefore, one might expect them to be fairly resistant 

 to its influence. However, an experiment by Miss Ferguson^ tends 

 to show that light has an inhibitory effect on the germination of 

 the spores Psalliota caiwpestris. 



In order to test the effect of sunlight upon the vitality of the 

 spores of Schizophylluin commune, which are colourless, I proceeded 

 as follows. A fruit-body was revived in the manner to be described 

 in Chapter IX., and, when shedding spores, it was set in a closed 

 chamber (cf. Fig. 37, p. '.)7), at the bottom of which were two glass 

 slides lying side by side. In the course of a night the slides became 

 thinly and evenly coated with a spore-deposit, and next morning 

 they were removed from the chamber. One of them was then 

 supported by a clamp-stand so that it was freely exposed to the 

 direct action of the sunlight streamino' throutjh a window in the 

 laboratory, and the other was kept in the dark. The temperature 

 of the laboratory was about 19° C. Tests for germination were made 

 by placing the spores in hanging drops of a neutralised nutrient 

 medium consisting of 1 per cent, glucose, 1 per cent, peptone, 

 0'3 per cent, meat extract, 0'5 per cent, sodium chloride, and 10 per 

 cent, gelatine. The ring chambers containing the drops were 

 partially filled with distilled water, and were kept in the dark. 

 Comparative tests made during the month of April showed that 

 spores which had been exposed to sunlight for eight hours germi- 

 nated more slowly than spores which had been exposed to sunlight 

 for two hours, and these more slowly than those which had been kept 

 in the dark. Spores kept in the dark germinated about twenty 

 hours sooner than those which had been exposed to sunlight for 

 seven or eight hours. After three days the mycelia produced from 

 spores which had been kept in the dark were much more advanced 

 than those which had been produced from spores which had been 

 exposed to sunlight for periods of one, two, three, six, seven, and 

 eight hours respectively. It was also found that exposure of the 



^ Miss M. C. Ferguson, " A Preliminary Study of the Germination of the 

 Spores of Ayaricus campestris and other Basidiomycetous Fungi," U.S. Dep. of 

 Agric, Bureau of Plant Industry, Bull. No. 16, 1902, p. 21. 



