Vol. XXX, No. 9 
804 
Jo u rn al of Agricultural Research 
The amount of decay during the first 
day is much less than in the succeeding 
days, as would be expected. This may 
be accounted for (1) because some time 
is required for the fungus to become 
established on its new medium, and (2) 
because the operating surface increases 
rapidly with the lapse of time. Theo¬ 
retically, because of the increasing op¬ 
erating surface, each succeeding inter¬ 
val of time should show an increased 
amount of decay. The data (Table III 
and fig. 9) in connection with R. tritici 
show this tendency, but not consist¬ 
ently. This inconsistency may be ex¬ 
plained in part by the fact that in the 
later stages of decay there is a definite 
limit because of the size of the potatoes. 
would seem to indicate that the method 
employed here will give reasonably ac¬ 
curate results. It is true that some of 
the curves show some decided breaks, 
but the results taken as a whole are 
fairly consistent. It is not expected 
that they would be so uniform as those 
obtained in culture media, for here 
there are two organisms to be dealt with 
instead of one. Erratic behavior, so 
far as infection and the amount of de¬ 
cay in individual potatoes is concerned, 
is often observed. More uniform re¬ 
sults probably would be obtained if a 
larger number of potatoes were em¬ 
ployed, but the time element in setting 
up a particular experiment then be¬ 
comes a source of error. 
/70 
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,2 3 5 6, ,2 3 5 6, 
3°C. /4.5°C. 
2 3 56, 
J 2 3. J 23. ,/ 2 3, 
J 2 35 6, J 2 3 i ^2 3, _ ^ 
23°C. 243°C. 283°C. 32*0 34~5°C 3?.5°C. 
Time in days and temperature in °C. 
Fig. 9.—Graph showing the amount of decay by Ehizopus tritici at various temperatures and at different 
intervals of time 
The extreme variation in the opti¬ 
mum temperatures given for the succes¬ 
sive periods of time for any of the 
species is as follows: Rhizopus reflexus , 
4.5° C. (Table III and fig. 7); R. nigri¬ 
cans , 3° (Tables III and IV and fig. 6); 
R. tritici , 2.5°, but is identical in two 
cases (Table III and fig. 3); R. maydis, 
2° (Table III and fig. 5); R. artocarpi, 
1° (Table III and fig. 8); and R. oryzae , 
0° (Table III and fig. 4). This fact 
The increase in the amount of decay 
with the rise in temperature is consis¬ 
tently high throughout these experi¬ 
ments as well as in the second type of 
experiment, higher as a rule than where 
other methods of measurements are 
employed, but it represents more 
nearly the actual loss involved than 
where the diameter of a spot is used as 
a measurement of the amount of decay; 
and even where the decay is a surface 
