194 
the blotches continued to increase in size, ultimately attaining a 
diameter* of about one-sixth of an inch, and at the same time 
becoming sunk or depressed below the general surface. When 
this stage is reached, if the apple is pared, a rust-coloured patch 
of flesh is found underlying each blotch. Microscopic examination 
showed the cells composing the rust-coloured patches to be dead 
and collapsed — hence the depressions— and crowded with starch 
grains, whereas the starch had entirely disappeared from the 
healthy cells in the process of ripening. 
Neither fungi nor insects play any part in the disease under 
consideration, which is of a purely physiological nature, and in 
i due to irregularities in the 
To make this point clear, a brief explanation of the changes 
that take pla .. u i i the combined causes, is 
necessary. When an a and emering on the 
i-ipeimm- period, it contains ;i considerable amount of malic acid 
respectively into other 
It is important to remember that the rate of respiration or 
n l" nil >- dep< nds dm - - rir, h on temp, rature, and the amount 
of oxygen present in the air to which the fruit is exposed. When 
conditions are favourable for ripening, the malic acid is oxvdised 
- iir-.\ followed l,y the Kr ;l .-cli. Wlini the temperature 
is high, the acid oxydises verv .juickdv and fermentation com- 
mences, which often kills the cells and thus prevents further 
ripening. This is exactly what has happened to the fruit under 
m Owing to excess of temperature during the early 
period of ripening, certain groups of cells were killed by fermen- 
tation commencing before the starch was converted into sugar, 
which resulted in the dead, rusty patches of flesh. Starch is most 
abundant near the periphery of the apple, and is almost absent 
towards the centre; this is why the rusty, dead patches always 
occur just under the skin. . 
On the other hand, when fruit is kept at a temperature not 
exceeding 35 F., ripening proceeds normally, as the aeid is not 
oxydised sufficiently quickly to set up fermentation at too early a 
The relativ 
amount of oxygen present in the air determines t 
a reat ex.ent the operation of ripening, as respiration depends u 
the presence of this element, and in some modern fruit rooms 
only a sufficient amount of oxygen is allowed to be present in the 
w i * P . the . fruit J T u8t alive > when the object is to retard the 
period of ripening Judging from results already arrived at it 
Tnfht f aPP > af -n ' «"> s"PPly of oxygen 
■L™ r °T' Tl 11 ' m the near future ' be the most important 
tactor concerned in the process of ripening fruit. 
