58 STIMULATIVE INFLUENCES. 



the cultures under a brief illumination by a powerful electx-ic 

 arc, this worker ascertained that considerable acceleration of 

 respiration is experienced in the case of Oidiuvi ladis, Asper- 

 gillus nhjf'Y, and one species each of Muc.or and Penicillium. 



The action of sunlight has been the object of a number of 

 observations, which merit our attention the more in that they 

 were chiefly made with yeasts, and partly relate to the biology 

 of the fungoid flora of the vine. Of the other fungi, Asjienjillus 

 glaucus was examined by Elfvixg (I.) in this connection, whereby 

 it appears that the conidia when ripe will stand insolation for 

 several weeks in succession at the latitude of Helsingfors, with- 

 out injury, though they are killed in a few days when in a 

 young, immature condition. Far inferior powei's of resistance 

 were presented by the yeasts subjected to insolation in the 

 south of France by V. Mautinaxd (II.), whose results were 

 afterwards confirmed by G. Tolomei (YIL). It was found that 

 both sporogenic and sporeless cells in two races of the group 

 Saccharomyces eUipsoideus, and also cells of S. apiculatus, 

 perished after four hours' exposure to the sun's rays at an 

 atmospheric temperature of 41° to 45° C. A similar result 

 followed insolation for three days at 36° to 37' C, whereas 

 other specimens of the same species remained alive when kept 

 in the dark under otherwise equal conditions. This coincides 

 with the results of the experiments made by W. Lohmanx (I.) 

 with Sarcliaromyces Pastovianus I. Hansen, two species of I'orula, 

 two film-yeasts {Mijcoderma), and a distillery yeast (Race II. of 

 the Berlin Experimental Station), these organisms being killed 

 in a few hours by insolation, as well as by illumination with an 

 electric arc lamp of 8000 to 11,540 metric candle power. The 

 last-named culture yeast succumbed first, whereas the first of 

 the wild yeasts proved the most resistant. The unfavourable 

 conditions artificially produced by Martinand are experienced in 

 piuctical viticulture by the yeast cells that make their habitat 

 on the grapes most fully exposed to the sun, i.e. particularly 

 those on the upper part of the vine-stocks. Consequently we 

 should expect to find in that position a smaller number of 

 living cells than on the grapes lower down. This observation 

 of Martinand's also leads to the conclusion that the grapes from 

 southei-n countries — which often give very poor fermentation — 

 are less al)undantly inliabited by yeast cells, and are chiefly 

 infested by such races as are less sensitive to insolation. It is 

 therefore probable, as a result of this factor of natural selection, 

 that the wine yeasts of southein latitudes are physiologically 

 different from those whose progenitors have lived for centuries 

 under a cooler sky. 



An assertion deserving closer investigation is that of Ward 

 (VII.), to the effect that the colouiing matters of chromatic 

 fungi iifford protection against the injurious influence of light. 



