Culture of Verticillium cilbo-atruni , B. et Br. 
53i 
Aeration. 
The effect of aeration was studied by aerating a series of culture flasks 
continuously, and determining at regular intervals the dry weight of 
mycelium produced. These experiments were all carried on at 2 i°C. in 
a large incubator, and the flasks were aerated with the help of a blast pump 
connected with the water supply. Control non-aerated flasks were placed 
in the same incubator. In the first set of experiments, the flasks were 
Fig. 8. Photographs of cultures of V. albo-atrum after fifteen days at 12 0 , 14 0 , 
16°, 18°, 21 0 , 22.5 0 , 25 0 , and 27°C. 
aerated discontinuously, once for three minutes daily, and at the same time 
a series of flasks were shaken. The aerated ones were found to show less 
growth than the non-aerated ones, and about the same as those shaken. 
For five successive weeks a number of flasks were taken, and dry weights 
determined, and each time the aerated ones gave less growth, as did the 
shaken flasks. Obviously, the fungal hyphae were torn by the direct shak¬ 
ing or by that caused by rapid bubbling and this retarded growth. It was 
also found in this connexion that the best growth had taken place by the 
