268 Brown . — On the Germination and Growth of 
Of all the fungi tested, Penicillium glancum is the most insensitive to 
carbon dioxide. When we remember that, in the case of an atmosphere 
which gave 95 per cent. C 0 2 on analysis, the bulk of the remaining 
5 per cent, is nitrogen, it follows that limited supply of oxygen was now 
probably entering in as a factor. It is fairly doubtful, therefore, if Penicillium 
glaucum can be inhibited entirely by carbon dioxide alone — that is, within 
the limits of one atmosphere pressure. This again illustrates the very 
marked resistance of this organism to external conditions. 
The effect of nutrient in relation to the inhibition of germination by 
carbon dioxide is again shown in the above table. 
Speaking generally, we may say that the concentration of carbon 
dioxide which inhibits germination of fungal spores at ordinary temperatures 
lies in the neighbourhood of 20-30 per cent, when the spores are sown in 
water, and in the neighbourhood of 50-60 per cent, when the spores are 
sown in a good nutrient. These concentrations are not admissible in the 
practice of the gas storage method, and therefore inhibition of germination 
of the fungal spores cannot be realized under practical conditions. It 
remains to examine the degree of retardation which can be effected by 
concentrations which do not exceed 20 per cent., and especially to determine 
what effect as regards retardation can be brought about by the combined 
action of moderate concentrations of carbon dioxide and of low temperature. 
The remaining part of the experimental work may be divided into 
three sections, dealing with the combined action of carbon dioxide and low 
temperature upon (a) germination of fungal spores, (b) rate of growth of 
fungal colonies on artificial media, (c) rate of growth of specific fungi on 
certain fruits. 
A. Rate of Germination of Fungal Spores at different Temperatures 
and in different Concentrations of Carbon Dioxide. 
Experiments were carried out with spores of Botrytis cinerea . B. para- 
sitica , Penicillium glaucum , and Fusarium sp. Sowings of spores were made 
on the following media : 1 potato agar, apple gelatine, prune gelatine, and 
Richard’s solution with agar. These media were liquefied by heat and just 
before solidification were mixed with a few drops of a dense spore suspension, 
and then drops of the medium spread out on glass slides. The latter were 
then set up in moist containers and germination carried out in air and in 
air containing 10 per cent, and 20 per cent. C 0 2 . One series was run at 
1 5° and another at 5 0 . At intervals the average length of the germ-tubes 
was determined by micrometer counts. The carbon dioxide atmospheres 
1 The nutrient media were prepared in the usual way. Agar media had 1.5 % agar; gelatine 
media had 15 % gelatine. In the case of Richard’s solution with agar, the nutrient and the agar require 
to be heated separately and mixed when nearly cool. The various plant decoctions were prepared 
according to the conventional standards suggested by Duggar (Fungous Diseases of Plants, p. 24, 1909). 
