6 4 
Journal of Agricultural Research 
Vol. II, No. i 
for the pycnidia of this fungus to appear was at the very edge of the original spot. In 
experiment 2, 7 spots, and in experiment 4, 2 spots had enlargements 4 mm. in width, 
with tufts of Alternaria hyphae on their surfaces. All the enlargements were strikingly 
zonate. 
In the experiments of September 24 the leaves of York Imperial branches received 
the same treatment as in the experiments of September 17, both as to sterilization 
and spotting. In experiments 1 to 3 the leaves were sprayed with distilled water con¬ 
taining spores of Phomopsis, Sphaeropsis, and Alternaria, respectively, while in No. 
4, the check, they were sprayed with sterile water only. All the branches were then 
placed under bell jars lined with wet filter paper. The results after five days are 
given in Table IX. No attempts at reisolation were made. 
Table IX.— Results of inoculation experiment of September 24 on York Imperial apple 
branches. 
Experiment No. 
Number of 
burned 
spots. 
Number of 
enlarged 
spots. 
Average 
width of 
enlarge¬ 
ments. 
Percentage 
of enlarged 
spots. 
Mm. 
99 
2 
1 
2 
71 
3 
X 
4 
3 . 
102 
47 
I 
46 
4 . 
51 
4 
I 
8 
It will be noticed that, owing to the natural prevalence of Alternaria 
on the leaves, sterilization was quite difficult. From the writer's 
experience in making cultures from fruit, leaves, and twigs of apples 
grown in the South, he believes Alternaria to be the most widely dis¬ 
tributed fungus on the apple in that section of the country. In order 
to make the amount of natural infection about the same in all cases, all 
blanches used in a series of experiments were sterilized together so that 
each leaf received the same treatment. 
Table X. —Summary of results from all experiments in which sterilized leaves were used. 
Treatment. 
Number of 
burned 
spots. 
Number of 
enlarged 
spots. 
Percentage 
of enlarged 
spots. 
Sprayed with spores of— 
Coniothyrium. 
471 
123 
27 
Sphaeropsis. 
332 
46 
14 
Alternaria. 
864 
536 
62 
Phomopsis. 
2 59 
6 
2 
Coryneum. 
83 
9 
II 
Monochaetia. 
65 
3 
5 
Sprayed with sterile water. 
928 
62 
7 
The enlargements induced in each series of experiments bore a remark¬ 
able resemblance to the enlarged leaf-spot or frog-eye disease of the 
South. As shown in Plate VII, figure 3, the zonate effect was quite pro¬ 
nounced. This, as in the natural frog-eye, was due to an alternation of 
gray and brown coloration. Sometimes, adso, the zone extended com¬ 
pletely around the original spot, and sometimes its center lay at the 
margin of a spot, as is the case with frog-eye disease in nature. Alter¬ 
naria was the only fungus isolated with any degree of consistency from 
any of these zones. 
