38 



Prof. Marshall Ward. Experiments on the [Feb. 16, 



conidia of Botrytis cinerea will not develop in daylight. If tlie 

 conidial branches are not completed before sunrise, the whole process 

 stops till the darkness comes on again, and this, no matter when the 

 sowings are made. Klein also proved that this inhibition is due to 

 the blue-violet rays, and is in abeyance in proportion as they are 

 removed. 



Here, then, we have the light action effective in preventing the 

 storage of the spore materials, just as it is in germination in prevent- 

 ing their return into the area ©f metabolic activity. 



Sorokin found (' Botan. Jahresbericht,' 1874, p. 214) that if fresh 

 horse- dung is placed under screens of white glass, bichromate of 

 potassium, and ammoniated cupric oxide, in the light, for twenty-five 

 days, and compared with one another and with specimens in the dark, 

 the feeblest crops of fungi were obtained in the blue light. 



Laurent (* Comptes Rend. Soc. roy. de Bot. de Belgique,' T. 28 (2), 



1889, p. 162) exposed spores of JJstilago carbo in glass flasks to 

 direct sunlight, in July, and found eight hours' insolation killed them ; 

 whereas the controls were all right, and sixteen hours' insolation 

 behind a screen of quinine sulphate, cutting off the ultra-violet, did 

 not prevent their germination. The spores of Aspergillus niger, A. 

 glaucus, Botrytis cinerea, and Gladosporium proved much more re- 

 sistant. The spores of Penicillium were also found to succumb to 

 insolation. 



Elfving found (' Studien iiber die Einw. d. Lichtes auf die Pilze/ 



1890, p. 105) that intense sunlight in summer inhibited the germina- 

 tion of Aspergillus, but even several days or weeks of insolation did 

 not kill the fully ripe spores. If they had begun to germinate, how- 

 ever, the first germinal stages were very sensitive to sunlight ; and 

 they were equally sensitive when just developed, i.e., just before 

 ripening. 



The whole tenor of Elfving's work, which is more particularly con- 

 cerned with the vegetative mycelia and the weight of substance 

 developed, is to show that light inhibits the metabolic processes the 

 younger the tissues are, and the more the absorbed food materials ap- 

 proximate to the raw state. This is not contradictory of my idea that 

 the light destroys such substances as oily reserve materials directly 

 in presence of oxygen, and there is nothing surprising in the 

 action being facilitated on the germination of the spore — no doubt 

 the most dangerous moment is that when the material begins to pass 

 into the area of metabolic activity in the germinal hypha. 



The consideration of the above and other facts led me to formulate 

 to myself the following hypothesis : — 



No plant exposes a reserve store of fatty food materials to the danger 

 of prolonged or intense insolation without a protective colour screen, 

 calculated to cut cut at least the blue-violet rays, as these rays would 



