Fungi at various Temperatures , &c. 261 
the fungus will grow is as high as 3-5 atmospheres, while the minimal 
pressure is well below 1 per cent, of an atmosphere. In some cases the 
minimal oxygen pressure is extraordinarily low, as for example o- 000 16 
per cent, for Bacillus subtilis . While obligate anaerobes have a very low 
oxygen maximum (0-003 P er cent * f° r Clostridium buty victim ), facultative 
anaerobes were found by Porodko to be as resistant to increased oxygen 
pressures as obligate aerobes, and in some cases more so. 
The general result of the work just cited, which is in agreement with 
earlier work on this subject, was to indicate that variations in the oxygen 
pressure would be found to be of little importance in connexion with the 
purposes of the present investigation. 
Finally, mention may be made of the work of Berghaus ( 18 ) and of 
Chlopin and Tammann ( 19 ), dealing with the effect of varying gas-pressure 
upon the growth of micro-organisms. According to these investigators the 
effect of mere varying pressure of a neutral gas (hydrogen or nitrogen) 
upon the growth of micro-organisms is negligible within very wide limits. 
Experimental Method. 
The various temperature conditions were obtained by means of ordinary 
Hearson incubators in the case of the higher temperatures (15— 25 0 ), and 
for lower temperatures (2-10 0 ) an automatically regulated small ‘ Isko ’ 
refrigerator was used. The temperature of the latter was controlled 
electrically by means of a toluene regulator and a relay which stopped and 
started a pump circulating sulphur dioxide. It was constant to within half 
a degree on either side of the mean value. 
As regards the setting up of fungal cultures in the various atmospheres, 
the technique described by Kidd ( 16 , p. 41 1) was followed throughout. 
Large glass containers of Si ~5 litres capacity (of the type employed as 
desiccators) were used as receptacles for the fungal cultures. The cultures 
intended for study, together with a little water to check evaporation, were 
placed in these, the lids luted down with ‘resin cerate’, and the required 
concentration of carbon dioxide in the internal atmosphere made up after 
the manner described by Kidd — that is, the containers were attached to an 
air-pump, the enclosed air exhausted to the necessary amount as measured 
by a manometer (7-5 cm. Hg vacuum for 10 percent., 15 cm. for 20 per cent., 
&c.), and the pressure again brought back to normal by the introduction 
of carbon dioxide gas from a cylinder. The latter gas on analysis gave 
98 per cent, purity, the remaining 2 per cent, not being absorbable in 
either alkali or in alkaline pyrogallol, and therefore being presumably 
nitrogen. 
The composition of the atmosphere in the containers was systematically 
tested and checked by analysis. For this purpose a large size of Haldane 
gas apparatus was used. By this means the percentage of carbon dioxide 
