644 
Journal of Agricultural Research 
Vol. XXI, No. 9 
occur over a flat surface. This last criticism could not hold, however, in 
the cases where a piece of fungous felt was placed upon the cut surface. 
Here infection was retarded but not inhibited. 
Table III .—Effect of healing upon decay of sweet potatoes 
Results. 
Date. 
Num¬ 
ber of 
pota¬ 
toes. 
Method of 
inoculation. 
Time 
healed. 
Con¬ 
trol 
halves 
de¬ 
cayed. 
Healed 
halves 
de¬ 
cayed. 
Effect 
of 
healing. 
Presence of 
cork layer 
demonstrated. 
Nov. 17, 1919. . 
1 
Felt placed 
24 hours. 
1 
I 
None. 
(") 
Do. 
Do. 
1 
I 
on sur¬ 
face. 
.do. 
.do. 
48 hours. 
3 days.. . 
4 days... 
7 days... 
11 days.. 
6 days. . . 
1 
I 
I 
I 
Retarding 
decay. 
.do. 
(") 
Cork layer 
starting. 
Distinct 
Do. 
I 
.do. 
I 
I 
.do. 
Do. 
I 
.do. 
1 
I 
.do. 
cork layer. 
Do. 
Do. 
I 
.do. 
I 
0 
Inhibited 
Do. 
Dec. 3, 1919. ... 
9 
Well metli- 
9 
9 
decay. 
None. 
(") 
Dec. 5, 1919- 
2 
od. 
.do. 
24 hours. 
2 
0 
Inhibited 
( n ) 
( a ) 
Do. 
1 
.do. 
4 days... 
24 hours. 
6 days... 
1 
0 
decay. 
.do. 
Dec. 12, 1919.. . 
Jan. 22,1920... 
10 
.do. 
10 
10 
None. 
V) 
( a ) 
4 
.do. 
4 
3 
Inhibited 
June 17, 1920.. . 
12 
.do. 
4 days... 
12 
12 
decay in 
1 case. 
Marked re- 
D i s t i ti c t 
Mar. 20, 1920... 
9 
.do. 
...do. 
9 
9 
tarding 
of decay. 
None. 
cork layer. 
(*> 
a Not examined or no cork layer found. 
In order to study the effect of healing upon infection when cut sweet 
potatoes were subjected to conditions more nearly approximating those 
to which they would normally be exposed, the following experiment was 
conducted. About bushel of medium-sized potatoes were washed 
with soap and water, halved, and then held for 6 days at a temperature 
of 30° to 32 0 C. and a relative humidity of about 93 as registered by a 
standardized Lambrecht’s polymeter. The potatoes were then divided 
into four lots. The healed surfaces of two lots were smeared with a 
heavy suspension of Rhizopus spores in tap water, using a soft camel's- 
hair brush. The other two lots (controls) were treated in exactly the 
same way, except that the healed surfaces were cut away to a depth 
about 5 mm. before the spores were applied. One lot from each of 
these two sets was placed in an incubator maintained at a temperature 
of 25 0 and a relative humidity of 96. The other two lots were placed 
