Oct. 2, I916 
Effect of Blackrot Fungus on the Apple 
33 
Table III. —Dry weights (in grams) of fractions 1, 2, and 3 in sterile checks and in 
artificial cultures of Sphaeropsis malorum after 34 days’ incubation 
Item. 
Fraction 1. 
Fraction 2. 
Fraction 3. j 
Total. 
Sterile check. 
0. 850 
. 470 
- . 3 8 o 
9. 270 
4. 170 
- 5. 100 
2.384 
3 - 065 
+ . 681 
12. 404 
7 - 705 
- 4.699 
Inoculated flask. 
Changes in fractions in the inoculated 
flasks... 
Percentage of gain or loss in inoculated 
flasks. 
-44. 7 
“55- 02 
+28- 55 
- 37-97 
It is unnecessary to point out that the conditions in an artificial inocula¬ 
tion upon finely ground pulp which has been sterilized under pressure differ 
fundamentally from those surrounding an infection of the whole fruit 
under natural conditions. Sterilization brings about a very considerable 
hydrolysis of disaccharids and of more complex carbohydrate materials, ‘ 
so that a much larger supply of reducing sugars is available to the fungus. 
The finely ground character of the material permit% the rapid penetration 
of the material by the fungus, and there is consequently an exceedingly 
rapid growth. The enzyms of the fruit are destroyed, but there is 
opportunity for rapid spontaneous oxidations as a result of the free 
access of air through the cotton plugs, as is evidenced by a loss of 0.196 
gm., or 1.55 per cent, of the dry weight of the check during the period of 
incubation. The inoculated flask meanwhile lost 4.699 gm., or 37.97 per 
cent, a loss almost 25 times as great as that occurring in the sterile 
control. 
In artificial inoculations there is a considerable increase in the amount 
of alcohol-ether-water-insoluble material constituting fraction 3. In the 
sample for which data are given in Table III, the dry weight of this 
fraction was 3.065 gm., as compared with 2,384 gm. in the normal tissue, 
a gain of 0.681 gm., or 28.55 per cent. These results afford further 
evidence of the fact brought out by the detailed analyses of naturally 
infected fruits, namely, that there is a very considerable conversion of 
soluble to insoluble material as a result of the activities of the fungus. 
This conversion takes place with greater rapidity in comparison with the 
loss of soluble constituents from fraction 2 in unsterilized fruits, since in 
the fruit entirely decayed as a result of natural infection a loss of 2.659 
gm. from fraction 2 was accompanied by a gain of 1.345 gm. in fraction 3, 
while in the artificial inoculations, a loss of 5.100 gm. from fraction 2 was 
accompanied by a gain of only 0.681 gm. in fraction 3. These very con¬ 
siderable differences indicate that there are large differences between the 
metabolic activities of the fungus when grown upon sterilized, aerated 
pulp and those occurring in natural infections. They emphasize the 
obvious fact that very great possibilities of error exist wherever one 
attempts to reason back from the results obtained with artificial cultures 
and to construct therefrom a picture of the life processes of a pathogenic 
organism pursuing its life cycle under natural conditions. 
55855°—16 - 3 
