Culture of Verticillium albo-atrum, B. et Br. 533 
medium being 4-3. No particular relation between growth and change of 
pH could be established. It was however observed that pH remains low 
when the media is aerated, though more growth takes place. 
Experiments were next carried on to find out how long the weight con¬ 
tinued to increase in the aerated and in the non-aerated cultures, and whether, 
when the growth had stopped in both, the total weight was the same. 
This experiment was carried on in two sections. In the first aerated and non- 
aerated flasks were inoculated and incubated at 2i° C., and dry weight 
3 5 7 9 11 13 13 IT 19 21 23 2.5 27 29 31 33 todays • 
Fig. 10 . Dry-weight production of V. albo-atrum in aerated and non-aerated Coon’s medium 
of normal strength (N/i), and in non-aerated Coon’s medium of half strength (N/ 2 ). 
determined every five days for twenty-five days. Inoculations were made 
every time with equally old cultures, generally three weeks old ones 
on potato mush in tubes. Eight flasks were taken every five days for deter¬ 
mination of the dry weight. In the third interval nine aerated flasks were 
lost accidentally, so for the remaining three intervals only five flasks could 
be examined at a time. This would cause a greater probable error, but 
fortunately the results were very good, the error being quite low. As the 
eighty flasks required for the two sets, aerated and non-aerated, could not be 
started at once owing to the limited space available, the experiment was 
begun first with aerated ones only (forty flasks), and as, at each interval of five 
days, eight were taken out, fresh non-aerated ones were put in their place, 
