434 EVENING DISCOURSES 
of the atmosphere surrounding the apple must affect the storage life. If 
there is no oxygen present, the apple must die, and if there is an excess of 
oxygen it will live at a more rapid rate. An increase in the percentage of 
carbon dioxide in the atmosphere should, in general, retard the changes 
taking place in the apple, since carbon dioxide is the principal product of 
these changes. The experiments made by Hardy and those associated 
with him fully confirmed these conclusions, and as a result of their re- 
searches a new method of storing apples, known as ‘ gas-storage,’ has been 
developed. 
The relation of respiration to the supply of oxygen is somewhat complex. 
Supernormal amounts of oxygen in the atmosphere accelerate the occurrence 
of the climacteric, while subnormal amounts delay it. If the oxygen in the 
air, normally 21 per cent., is reduced to 5 per cent., respiration is minimal, 
the climacteric is definitely retarded and the magnitude is also greatly re- 
duced. Moreover, in the later stages, oxygen appears to have a definite 
toxic action, and the maintenance of a subnormal concentration correspond- 
ingly prolongs the life of the fruit. 
The effect of carbon dioxide is most important. It has no great effect 
on respiration in the pre-climacteric state, it markedly delays the onset of 
the climacteric, and in the post-climacteric state it depresses the rate of 
respiration. ‘There is, however, a definite limit to the amount of carbon 
dioxide which apples can tolerate. If this limit is exceeded, a physiological 
disease known as brown-heart is produced. This disease was the cause 
of serious losses in shipments of apples from Australia and New Zealand 
before its cause was known. ; 
There are therefore two simple methods of prolonging the life of apples : 
the application of cold—but it must not be too cold or the apple will break 
down and die; and gas-storage—but there must not be too much carbon 
dioxide or brown-heart will result and the apples will perish. Clearly, a 
combination of the two is the best solution, and such a combination is the 
basis of the recently developed method of gas-storage. There is, how- 
ever, an interesting relationship between the permissible amount of carbon 
dioxide and the temperature : carbon dioxide reduces tolerance of cold, so 
that in its presence low-temperature breakdown occurs at temperatures 
which would otherwise be safe; while the lower the temperature, the 
smaller is the concentration of carbon dioxide that will produce brown- 
heart. 
Application of Gas-storage.—I now come to application. I have already 
said that English apples are not very tolerant of cold. While certain varieties 
may be kept for six months at a normal cold-storage temperature of, say, 
34° F., wastage from low-temperature breakdown occurs rapidly on removal 
from store—a serious matter, since, from a commercial point of view, 
an apple must keep in good condition for at least three weeks after 
removal from store to permit of marketing. Gas-storage has solved the 
difficulty. 
I give as an example that most important cooking apple, the Bramley’s 
Seedling. It was found that at a temperature of 41° F., well above the 
freezing-point, and with the oxygen in the atmosphere at ro per cent. and 
the carbon dioxide also at 10 per cent., Bramley’s Seedling apples could be 
kept in first-rate condition for twelve months, and, moreover, would retain 
their condition on removal from store for a period long enough to permit 
of marketing through the usual channels. This discovery, the work of 
Hardy and those associated with him, opened a new era in the storage of 
English apples, and one of which English growers were not slow to take 
advantage. ‘The discovery is but a few years old, but to-day there are no 
