1030 
Journal of Agricultural Research 
Vol. XXIV, No. la 
TablK V. —Effect of dry outer scale tissue of red, yellow, and white varieties of 
upon the spore germination of Colletotrichum circinans {experiment i) 
onion 
Germination. 
Variety. 
No 
germina¬ 
tion. 
Normal 
germina¬ 
tion. 
Ruptured 
germ 
tubes. 
Abnormal 
germ 
tubes. 
Swollen 
spores. 
Per cent. 
Per cent. 
Per cent. 
Per cent. 
Per cent. 
Red. 
0 
21 
78 
0 
I 
Yellow. 
0 
35 
61 
2 
2 
White. 
10 
90 
0 
0 
0 
TabIvE VI. —Effect of dry outer scale tissue of red, yellow, and white varieties of onion upon 
the germination of Colleto trichum circinans {experiment 2) 
Petri 
dish 
No. 
Color of tissue used. 
Germination. 
No germi¬ 
nation. 
Normal 
germina¬ 
tion. 
Ruptured 
germ 
tubes. 
Abnormal 
germ 
tubes. 
Swollen 
spores. 
Per cent. 
Per cent. 
Per cent. 
Per cent. 
Per cent. 
/Red. 
7 
2 
45 
42 
4 
I 
\ Control. 
9 
91 
0 
0 
0 
/Red. 
12 
0 
88 
0 
0 
2 
\Control. 
12 
88 
0 
0 
0 
/Yellow. 
34 
0 
66 
0 
0 
3 
\Control. 
7 
93 
0 
0 
0 
A 
J Yellow. 
24 
0 
76 
0 
0 
4 
t Control. 
II 
89 
0 
0 
0 
/White. 
8 
92 
0 
0 
0 
5 
\ Control. 
9 
91 
0 
0 
0 
/White. 
13 
87 
0 
0 
0 
0 
[Control. 
47 
53 
0 
0 
0 
EEEECT UPON GROWTH 
The experiments just described show conclusively that the water extract 
ofipigmented dry scales is highly toxic to spores of Colletotrichum circinans, 
while a similar extract from white scales has no such inhibitory effects. 
The fact that the toxic substance (or substances) is so readily diffusible 
leads one to surmise that the plant may be protected by its gradual solu¬ 
tion into the soil water immediately surrounding the bulb. The smudge 
organism develops normally in the soil; hence it is conceivable that in 
some cases at least the spore may germinate at some distance from the 
bulb; thus the mycelial hyphae may be the first to come into close con¬ 
tact with the bulb or with the soil solution immediately surrounding it. 
Accordingly an experiment was carried out to determine the effect of the 
pigmented extract upon the growth of the fungus mycelium. 
Spores were germinated in water until the germ tubes were several 
times the length of the spores. Small pieces of dry outer red scales were 
then added to certain of the drops, while others were left as controls. 
After 24 hours, examination showed that whereas the hyphae in the con¬ 
trol drops had continued to grow normally, those to which the bits of red 
scale had been added had grown little if at all from the time these pieces 
