120 Brown.—Experiments on the Growth of 
of medium is produced. Further, a plate of medium on exposure to 
a culture of Sphaeropsis is protected from staling, at any rate in the neigh¬ 
bourhood of the watch-glass, by the insertion between the two of a small 
watch-glass containing dilute acid., 
That the gas was ammonia was shown by its giving Nessler’s reaction. 
It was also identified by isolation as the chloride. Alkylamines might be 
present in small quantities, but they were not demonstrated. 
In order to be certain that the cultures producing the staling were 
absolutely free from any bacterial contamination (which cannot be guaran¬ 
teed in Petri dish cultures where the lids have been removed), the experi¬ 
ments were carried out with pure tube-cultures of the staling fungus. The 
medium to be staled was used in the form of a film on sterilized slides. 
The results obtained were identical with those already described. 
The amount of ammonia present in tube cultures was determined for 
a number of media. The tubes contained 25 c.c. of the medium, half of 
them being inoculated with Sphaeropsis , the other half left uninoculated. 
After four weeks’ growth (at 18 0 C.) of the inoculated tubes, the contents of 
each tube were distilled over magnesia, and the distillate collected in deci- 
normal sulphuric acid. The amount of alkaline gas passing over was then 
determined by titrating against decinormal alkali. The figures in the table 
represent cubic centimetres of decinormal solution. For each medium, eight 
tubes were analysed, i. e. four inoculated and four uninoculated. The 
results, which showed good agreement among themselves, gave the average 
values shown in the following table: 
Table VII. 
Agar 1.5 °/ 0 ; 
Medium. 
Potato agar 
Potato gelatine 
Richards’ solution (KN 0 3 i °/ Q ) with agar 
„ „ (KN 0 3 1 °/ 0 ) with gelatine 
„ „ (KN 0 3 o.r°/ 0 ) with agar 
,, „ (KN 0 3 0.1 °/ Q ) wi th gelatine 
elatine io °/ 0 . 
Amount of Alkaline Distillate from 
Inoculated Tubes. Uninoculated Tithes. 
3-03 
0.98 
ir -7 
2.03 
o -5 
0-17 
9-3 
o -3 
0-28 
0.13 
1 3*55 
0.6 
We see here that there is a moderate amount of ammonia present 
in the cultures on potato agar, and much more on all the cultures of 
gelatine media (including, from other experiments, apple gelatine). The 
small quantities obtained with the two Richards’ solutions plus agar fall 
within the experimental error limits of the determinations. Though 
the amount of ammonia present in these gelatine media is considerable, 
it is not ail present in the free state, being neutralized up to a certain limit 
by the acidity of the nutrient solution and of the gelatine itself. With 
media such as apple gelatine and Richards’ solution gelatine, where the 
nutrient solution is itself fairly acid, free ammonia is late in appearing in the 
