jan. 15,1925 Further Studies on Toxicity of Extracted Onion Juice 185 
Table VI.— The effect of the volatile components of onion extract on the spore 
germination of several fungi 
Percentage of germination 
Organism 
Colletotrichum circinans _ 
Colletotrichum lindemuthianum 
Colletotrichum trifolii . 
Colletotrichum pisi _ 
Olomerella cingulata . 
Botrytis allii ___ 
Botrytis 108a .. 
Botrytis cinerea .. 
Fusarium cepae _ 
Fusarium No. 45 (onion). 
Fusarium graminearum . 
Aspergillus niger _ .. 
Aspergillus 4660 _ 
Number of drops of onion juice in chamber 
Con- 
trol 
5 
4 
3 
2 
1 
0.5 
0.1 
0.01 
0.001 
0 
0 
0 
0 
0 
65 
68 
41 
74 
86 
0 
0 
0 
0 
0 
0 
77 
60 
64 
57 
0 
0 
0 
0 
40 
17 
30 
27 
38 
0 
90 
89 
97 
100 
100 
100 
100 
100 
100 
0 
0 
87 
87 
76 
75 
72 
73 
61 
74 
78 
71 
98 
96 
86 
92 
91 
86 
84 
97 
90 
90 
95 
100 
100 
100 
100 
100 
100 
71 
78 
83 
63 
37 
23 
9 
29 
24 
30 
95 
95 
98 
93 
92 
96 
93 
94 
98 
30 
64 
86 
70 
94 
94» 
96 
89 
0 
0 
0 
0 
100 
95 
90 
97 
96 
98 
0 
9 
80 
68 
90 
95 
93 
94 
83 
93 
48 
99 
99 
100 
100 
100 
100 
100 
100 
is pertinent to the relative importance 
of the latter in determining the degree 
of parasitism. There are several para¬ 
sites of the onion bulb which vary in 
the mode and the aggressiveness of 
their attack. Colletotrichum circinans 
penetrates the cuticle readily at any 
point but once having gained entrance 
progresses very slowly, although it is 
not devoid of cellulose-digesting prop¬ 
erties. Botrytis allii does not readily 
enter the unbroken surface but almost 
always enters through wounds or 
through dead neck tissues. Once within 
the host it readily kills the tissue 
slightly in advance of the hyphae and 
it is a much more aggressive parasite 
than Colletotrichum circinans . Fusar¬ 
ium cepae and Fusarium sp. 45 also 
gain entrance principally through 
wounds but cause very rapid decay 
having once entered. Two species of 
Aspergillus offer a similar contrast. 
One (A. niger) is very superficial and 
only mildly parasitic, while the other 
(.Aspergillus sp. 4660) decays the tissue 
very rapidly. 
These differences may originate in 
food relations, enzyme production by 
the invader, or antagonistic substances 
within the host. The present study is 
limited to the last question and has 
sought to determine what differential 
reactions on the part of bulb-rotting 
fungi and their allies occur in relation 
to toxic substances in onion tissue. 
Inquiry into the nature of the inhib¬ 
itory substances in the fleshy scales of 
the onion bulb shows that they are of 
at least two kinds. One type present 
in extracted juice is not readily re¬ 
moved or broken down by boiling and 
Table VII.— The effect of the volatile components of onion extract on the growth of 
sporelings of several fungi 
Length of germ tubes (microns) 
Organism 
Number of drops of onion juice in chamber 
Con¬ 
5 
4 
3 
2 
1 
0.5 
0.1 
0.01 
0.001 
trol 
Colletotrichum circinans ... 
0 
0 
0 
0 
0 
22 
28 
25 
43 
72 
Colletotrichum lindemuthianum 
0 
0 
0 
0 
0 
0 
12 
21 
29 
25 
Colletotrichum trifolii _ _ 
0 
0 
0 
0 
6 
9 
13 
14 
0 
12 
Colletotrichum pisi _ 
0 
10 
11 
14 
51 
66 
84 
85 
83 
88 
Olomerella cingulata. _ . _ _ 
0 
0 
4 
8 
11 
25 
27 
36 
31 
32 
Botrytis allii ....... 
39 
39 
69 
74 
115 
149 
180 
171 
191 
180 
Botrytis 108a „ _ 
151 
197 
215 
184 
228 
197 
176 
223 
185 
Botrytis cinerea _ ____ 
14 
22 
21 
35 
57 
50 
58 
80 
62 
50 
Fusarium cepae ___ 
18 
25 
39 
45 
48 
48 
45 
40 
46 
Fusarium 45 (onion)__ 
18 
16 
25 
26 
24 
22 
25 
23 
Fusarium graminearum _ 
0 
—o' 
0 
0 
44 
90 
132 
166 
170 
170 
Aspergillus niger .. 
0 
5 
29 
22 
71 
73 
85 
135 
112 
111 
AspergiUus 4660. ... 
38 
35 
43 
43 
64 
64 
80 
80 
0 
87 
