146 
Journal of Agricultural Research 
Vol. VIII, No. 4 
The contrasts between the temperature responses of the different fungi 
are very striking. Sclerotinia cinerea is the most rapid rot-producing 
organism tested and is less inhibited by cold than most of the other 
fungi. Sphaeropsis malorum is in general more rapid than Penicillium 
expansum; but the former is practically inhibited at o°, while the latter 
can make little growth at 30°. The low optimum and slow rate of 
growth with Neofabraea malicorticis are particularly interesting. 
The contrasting results at the different temperatures are shown in 
graphic manner 
in Plates 2 and 3. 
In figures 1,2, 
and 3 the diam¬ 
eter of the rot is 
taken as the basis 
of comparison. 
This does not 
give the real con¬ 
trast in size of rot 
or in the amount 
of work done by 
the fungus. A 
comparison of 
the temperature 
effects on a chem¬ 
ical or physiolog¬ 
ical basis would 
require that the 
volume of the rot 
be considered 
rather than the 
diameter. Simi- 
Fig. 3 . —Graph showing the development of rot on Winesap apples. The | aJ * volumes have 
curves show the average weekly increase in diameter. With Sclerotinia 
cinerea , Sphaeropsis malorum, and Volutella fructi they are based on records the Same ratio 
made two weeks after inoculation; with the other fungi on records made each Other as 
three weeks after inoculation. t . . 
the cubes of their 
like dimensions, but unfortunately the masses of rotted tissue do not 
have similar shapes at the different stages in their development. The 
fungus can not spread outward, and it usually spreads laterally more rap¬ 
idly than it does toward the core, thus making the area of the rot a fairly 
close index of its volume. In figure 4 the curves are plotted on the basis 
of the average rot areas at the different temperatures. It will be noted 
that in most cases the increase in growth with a io° rise in temperature 
comes within the range of the Van’t Hoff law; but there are several 
striking exceptions, Sphaeropsis malorum producing a rot area 24 times 
