Jan. 15,1925 Further Studies on Toxicity of Extracted Onion Juice 183 
Table V .—The effect of concentration of expressed onion juice upon germination 
and growth of various fungi 
Organism 
Expressed onion juice 
Onion 
decoc¬ 
tion 
Un¬ 
diluted 
Diluted 
1 to 1 
Diluted 
1 to 10 
Diluted 
1 to 100 
Diluted 
1 to 
1,000 
Colletotrichum circinans: 
Percentage germination... 
0 
0 
0 
91 
89 
84 
Average length germ tube (microns)... 
0 
0 
0 
123 
164 
165 
Colletotrichum lindemuthianum: 
Percentage germination.. 
0 
0 
0 
0 
1 
57 
Average length germ tube (microns)_ 
0 
0 
0 
0 
25 
Colletotrichum pisi: 
Percentage germination.... 
0 
0 
0 
60 
88 
100 
Average length germ tube (microns)__ 
0 
0 
0 
11 
15 
Glomerella cingulata: 
Percentage germination.. 
0 
28 
50 
26 
56 
75 
Average length germ tube (microns)_ 
0 
1 
1 
1 
2 
37 
Botrytis allii: 
Percentage germination___ 
5 
99 
100 
100 
100 
100 
Average length germ tube (microns)_ 
62 
85 
200 
200+ 
500+ 
500+ 
Botrytis 108a: 
Percentage germination.. 
0 
99 
100 
100 
100 
100 
Average length germ tube (microns)_ 
0 
300+ 
500+ 
500+ 
500+ 
500+ 
Botrytis cinerea: 
Percentage germination____ 
0 
0 
80 
100 
100 
100 
Average length germ tube (microns)__ 
0 
0 
9 
244 
500+ 
500+ 
Fusarium No. 45 (onion): 
Percentage germination___ 
0 
6 
14 
62 
89 
88 
Average length germ tube (microns)_ __ 
0 
10 
8 
14 
29 
22 
Fusarium cepae: 
Percentage germination_____ 
0 
0 
1 
99 
98 
94 
Average length germ tube (microns)_ 
0 
0 
22 
54 
89 
34 
Fusarium graminearum: 
Percentage germination... 
0 
0 
1 
95 
96 
100 
Average length germ tube (microns)_ 
0 
0 
12 
33 
75 
137 
Aspergillus 4060: 
Percentage germination.__ 
0 
0 
93 
100 
Average lenght germ tube (microns).. . 
0 
0 
26 
87 
Aspergillus niger: 
Percentage germination... 
0 
0 
0 
62 
43 
85 
Average length germ tube (microns)__ 
0 
0 
0 
24 
33 
145 
Aspergillus niger) show little or no 
germination and growth below the 1 to 
100 dilution. In correlation with this 
fact it is found that the last two fungi 
neither occur as natural wound para¬ 
sites nor do they cause infection when 
artificially inoculated into wounds. 
The other four organisms are normally 
wound parasites. As already noted by 
Walker and Tims (8), inoculation of 
onion bulbs with Fusarium cepae by 
injecting spores into fresh needle 
wounds usually yields negative results, 
unless the bulbs are kept in moist 
chambers for about 48 hours after 
inoculation. The exact nature of this 
phenomenon needs further study. It 
is probable that the cell sap exuding 
into a fresh wound has a great deal to 
do with the inhibition of this organism, 
which becomes a vigorous parasite 
when once established in the host tissue. 
Similarly the writers have noted in 
inoculation experiments with Botrytis 
allii that when onion bulbs, the necks 
of which have been clipped so as to 
expose freshly exuding cell sap, are 
sprayed with a spore suspension, some¬ 
times an unusually small percentage of 
bulbs becomes diseased. When these 
organisms become established as in 
nature, either in somewhat more dilute 
cell sap or in meteoric water on the 
surface of the dead tissue at the neck 
of the bulb, it is evident that they 
overcome the toxic effects sufficiently 
to make progress. 
EFFECT OF VOLATILE SUBSTANCES 
UPON GERMINATION AND GROWTH 
Preliminary experiments on the ef¬ 
fect of volatile onion oil upon germina¬ 
tion and growth showed that all 
species were somewhat retarded. Fol¬ 
lowing the methods already outlined 
and providing as uniform conditions 
as possible, the fungi were compared 
by using spores from fresh cultures, 
and exposing them to various amounts 
of toxin from a common source at a 
temperature of 25° C. Although many 
repetitions of this experiment were 
made, one representative set of data 
is presented for consideration. The 
results on spore germination are given 
in Table VI and those on growth of 
the sporelings in Table VII. 
