162 
Journal of Agricultural Research 
Vol. VIII, No. 4 
pared with delayed storage. Most of the rot fungi are able to make but 
a very slow growth at o° and 5 0 if placed at once at those temperatures; 
but if they go into storage with the accumulated energy of a week’s 
growth or more the results are likely to be very different. 
With the weakest parasites the maturity of the fruit has also had a 
modifying effect, the fungi having a lower minimum on the ripe than on 
the green fruit. This was evident with the apples of a particular variety 
inoculated at the same time and is also the most probable explanation 
for some of the contrasts in the results on the different varieties tested. 
At o° Penicillium expansum , for instance, was able to produce a measur¬ 
able rot on the York Imperial and Ben Davis by the end of 5 weeks, on 
the Yellow Newtown and Winesap that were slightly greener by the end 
of 8 weeks; but on still less mature York Imperial and Arkansas apples 
it had produced no rot at this temperature after 18 weeks. 
Experiments have shown that practically all of the rot fungi are able 
to germinate at 5 0 and most of them at o°. Germination is somewhat 
delayed at the latter temperature; but this does not seem to be the whole 
explanation for delayed growth on fruit at low temperatures, since in 
most of the experiments made time was given for germination before the 
fruit was placed in storage. It is of interest to note that while P. expan¬ 
sum was the first to germinate at o° it is comparatively slow in making a 
start on fruit at that temperature. With P. expansum and probably with 
others of the weaker parasites cold storage inhibits the initial stages of 
the rotting more than it does germination. 
While the minimum temperature for the various fungi has varied greatly 
with the food material, there has been little shifting of the optimum under 
the same conditions. Alternaria sp. and Fusarium radicicola have an 
optimum at 30° or above; Botrytis cinerea , Glomerella cingulata, Penicil¬ 
lium expansum , Sclerotinia cinerea , Sphaeropsis malorum and Voluiella 
fructi at 25 0 , and Cephalothecium roseum and Neofabraea malicorticis at 20°. 
The temperature curves are all plotted on the basis of diameter of the 
rot or of agar colony. On this basis the increased growth with a rise of 
temperature usually comes within the limits of the Van’t Hoff law, the 
diameter becoming two to three times greater with each io° rise in tem¬ 
perature; but as has already been pointed out, this method of estimation 
does not give full value to the increase in size in the larger rots and larger 
agar colonies. Curves plotted on the basis of area would come within the 
limits of the Van’t Hoff law in most cases; but there would be some 
striking exceptions, Sphaeropsis malorum producing a rot area 16 times 
*as great at 25 0 as at 15 0 , and Botrytis cinerea an area 25 times as great 
at 20 0 as at io°. 
SUMMARY AND CONCLUSION 
(1) The behavior of Alternaria sp., Botrytis cinerea , Cephalothecium 
roseum, Fusarium radicicola , Glomerella cingulata, Neofabraea malicorticis , 
Penicillium expansum, Sclerotinia cinerea , Sphaeropsis malorum , and 
