TEMPERATURE AND OXYGEN TENSION 111 



greater as temperature was increased, and at 29.5° C was critical. 

 The loss of carbon (as CO;.) was least within the range 25.5° to 

 29.5° C; it was relatively great at 17.5° and at 33.5° C. Moreover 

 the rate of C0 2 production per unit of mycelial area and the rate 

 of growth were quite alike within the range 17.5° to 29.5° C. 



TEMPERATURE AND OXYGEN TENSION 



In the light of findings that the respiratory quotient is highest 

 at the lowest temperatures and, conversely, lowest at the highest 

 temperature, it would be expected that oxygen tension would also 

 modify physiological processes. Evidence of such modifying 

 effect has been presented by Scheffer and Livingston (1937). 

 They grew Polystictus versicolor on malt agar in special tubes, 

 by means of which they could modify the oxygen tensions and 

 then keep them at constant levels. At the same time they main- 

 tained constant temperatures by means of thermostatically con- 

 trolled incubators. By these procedures they found that C0 2 

 production per unit area of mycelial mat was always most rapid 

 as 2 pressure became greater. At 33.5° C with 745-mm pres- 

 sure of 2 , C0 2 production was most rapid; it was least rapid at 

 17.5° C with zero 2 pressure. Mycelial growth, however, was 

 most rapid at the optimum temperature for P. versicolor, that is, 

 at 29.5° C, at all 2 pressures from 16 mm to 745 mm. When 

 C0 2 production in atmospheres of pure 2 was compared with 

 that in pure N 2 , Scheffer and Livingston noted that the rate per 

 unit of mycelial area was two to five times as rapid in oxygen as 

 in nitrogen. 



The availability of 2 is known to operate in another manner, 

 as has been demonstrated by Chaudhuri (1923). He aerated 

 liquid nutrient media on which Verticillhim albo-atram was being 

 grown at different temperatures, employing rate of spread as a 

 measure of yield of fungus material. His data show that aeration 

 markedly increases both the rate of growth and the total amount 

 of growth in a given volume of liquid media. Since V . albo- 

 atnnn is known to produce staling products, Chaudhuri postu- 

 lates that these increases are to be attributed to the oxidation of 

 w r aste products. 



