118 Brown.—Experiments on the Growth of 
With the same depth of pouring, some media are more readily staled 
than others, e. g. potato agar is more readily staled than potato gelatine 
(with the same concentration of potato extract in each), as is shown by the 
following figures, which represent two days’ growth of Sphaeropsis : 
Table IV. 
Unexposed. 
Potato agar (agar 1-5 %) 2-08 
Potato gelatine (gelatine 10 %) 1-84 
Exposed to 
Sphaeropsis 
Culture on 
Potato Agar. 
1.03 
1.83 
Any of the usual media (plum, prune, apple, &c.) made up with 
gelatine behave in the manner indicated. 
Under the same conditions some fungi are more easily staled than 
others. The following table (V) illustrates the behaviour of four fungi in 
this respect. The cultures used to produce the staling were Sphaeropsis 
on potato agar and potato gelatine, both series being of the same age. 
The exposed plates were of potato agar. The figures in round brackets 
represent the percentage growth, that on the unexposed plates being taken 
as 100. 
Fungus tested. 
Botrytis cinerea 
Sphaeropsis malorum 
Fusarium sp. 
Pen icillium glaucum 
Table V. 
Unexposed. 
1-82 (100) 
i-88 (too) 
1.52 (100) 
0-94 (100) 
Exposed to 
Sphaeropsis 
on P. A. 
0-64 (35) 
0.83 (44) 
1.18 (77) 
0.79 (84) 
Exposed to 
Sphaeropsis 
on P. G. 
o-o (o) 
o-o (o) 
0.74 (48) 
0.45 (48) 
A review of the experiments made on this point shows that Botrytis 
cinerea is more readily staled than Sphaeropsis , which again is more sensi¬ 
tive than either Fusarium or Penicillium. The two last are not definitely 
distinguishable in this respect. 
As to the nature of cultures showing staling, the magnitude of the 
effect depends on age. For the first few days it is negligible, then 
it reaches a maximum, and in old cultures it again becomes small. The 
period of most active evolution of ammonia was not accurately deter¬ 
mined, but the effect is usually well seen in cultures of ten days to a 
month. The effect appears sooner in shallow than in deep cultures, though 
after a time the latter show it just as strongly. 
The effect also depends on the fungus used. With potato agar as 
medium, Fusarium and Sphaeropsis produce staling in a marked degree, 
Botrytis only very slightly, and Monilia fructigena not at all. 
The composition of the medium on which the fungus is grown is of 
great importance. There is no evolution of staling gas from cultures on 
Richards’ solution with agar. 
