jan. 15,1925 Further Studies on Toxicity of Extracted Onion Juice 181 
germination of spores of Colletotrichum 
circinans so that no perceptible differ¬ 
ence in the toxic action at various 
temperatures resulted. As a further 
safeguard, however, practically all of 
the experiments were run at a constant 
temperature of 25°. 
result, under extremely moist condi¬ 
tions, and the cell lumen may be in¬ 
vaded before the cell collapses. Under 
ordinary storage conditions, however, 
the progress is very slow and at least 
in a majority of cases hyphae do not 
penetrate the living cells, but the latter 
Table IV .—Relation of temperature to the rate of depletion of the toxins in onion 
juice a 
Reaction of spores of Colletotrichum circinans 
Juice kept in ice box 
Juice kept at 25° C. 
Number of hours 
after extraction 
Reaction to volatile toxins 
Spores 
placed 
direct¬ 
ly in 
juice 
Reaction to volatile toxins 
Spores 
placed 
2 drops 
1 drop 
0.1 
drop 
0.01 
drop 
2 drops 
1 drop 
0.1 
drop 
0.01 
drop 
direct¬ 
ly in 
juice 
0 _.... 
0 
0 
0 
-f- 
0 
0 
0 
0 
4- 
0 
2 ... 
0 
0 
0 
+ 
+ 
0 
4.... 
0 
+ 
+ 
4* 
0 
8 .... 
0 
+ 
+ 
+ 
4* 
0 
15__ 
6 
0 
+ 
+ 
0 
+ 
+ 
+ 
+ 
0 
22 . 
0 
0 
+ 
+ 
0 
+ 
+ 
+ 
+ 
0 
46.. 
© 
+ 
+ 
0 
+ 
+ 
+ 
+ 
0 
90. 
0 
0 
“Symbols used: 0—no germination; ©= slight germination and retarded growth; — =* medium germi¬ 
nation and growth; +=good germination and growth. 
ORGANISMS USED AND THEIR MODE 
OF ATTACK 
For the extension of this study cer¬ 
tain of the more common onion bulb 
parasites were considered. These, with 
the smudge fungus, were representa¬ 
tives of the four genera, Colletotrichum, 
Fusarium, Botrytis, and Aspergillus. 
To further supplement the compara¬ 
tive study one or more species from 
each of the first three genera and one 
from Glomerella, all of which were 
nonpathogenic to the onion, were 
added. As introductory to a con¬ 
sideration of further experimental data, 
the existing knowledge of the mode of 
attack of each of the onion parasites 
will be reviewed. 
COLLETOTRICHUM 
The onion smudge organism ( Colle¬ 
totrichum circinans) and its method of 
infection have already been described 
( 6 ). Of importance in this connection 
is the fact that penetration always 
occurs directly through the cuticle by 
means of an infection hypha which is 
produced from an appressorium. Soft¬ 
ening and invasion of the cell wall 
show signs of degeneration and collapse 
before invasion actually occurs. It 
appears, therefore, that this fungus, 
even after infection, seldom actually 
invades the living cells. These studies 
were made with northern Globe varie¬ 
ties. More recent observations of the 
White Bermuda variety indicate that 
it may be parasitized more readily by 
C. circinans than the northern varieties, 
but this is a matter still under inves¬ 
tigation. 
Other species of Colletotrichum and 
Glomerella were picked at random for 
comparison with C. circinans , none of 
them being parasitic upon onion. 
BOTRYTIS 
The onion neck-rot fungus (Botrytis 
allii ) has been described by Munn (3). 
It is a wound parasite and ordinarily 
infects through injuries in the neck of 
the bulb. Munn has shown that this 
fungus secretes an enzyme which kills 
the bulb tissue in advance of the my¬ 
celium. Here also we have the organ¬ 
ism living out of immediate contact 
with the living host cell. 
A second species (Botrytis sp . 108a) 2 
commonly occurs on the outer scales of 
white onion, causing what is known as 
2 For the purposes of this paper this form will be referred to as Botrytis sp. 108a. A full description’ of 
the species will shortly be published. 
