Jan. 15,1925 Further Studies on Toxicity of Extracted Onion Juice 187 
7. In general, the reaction of each 
fungus followed the same trend for 
the dissolved as for the volatile toxins. 
8. Comparing onion pathogens and 
nonpathogens, there is no strict nega- 
tive correlation between pathogenicity 
upon onion and sensitiveness to the 
toxins, which only indicates that other 
factors enter into the determination 
of the parasitic relation. 
9. Considering the onion parasites as 
between themselves there is evident a 
negative correlation between aggres¬ 
siveness of parasitic attack and sensi¬ 
tiveness to the dissolved and volatile 
toxins. It is pointed out that the 
experimental results are not truly 
representative of the actual relation 
between host and parasite. The pre¬ 
sumption, however, is that as the par¬ 
asite invades the tissue the host toxins, 
though attenuated by fungous enzymes, 
may possibly exert some retarding 
effects upon the invader. If this be 
the case, it is suggested that the host 
toxins may be one of the numerous 
factors which determine the degree of 
parasitism attained by a given parasite. 
LITERATURE CITED 
(1) Brown, W. 
1917. ON THE PHYSIOLOGY OF PARASITISM. New 
Phytologist 16: 109-127. 
( 2 ) - 
1922. STUDIES IN THE PHYSIOLOGY OF PARASITISM. 
IX. THE EFFECT ON THE GERMINATION OF 
FUNGAL SPORES OF VOLATILE SUBSTANCES 
arising from plant tissues. Ann. Bot. 36: 
285-300. 
(3) Munn, M. T. 
1917. NECK-ROT DISEASE OF ONIONS. N. Y. State 
Agr. Exp. Sta. Bui. 437: 361-455, illus. 
(4) Semmler, F. W. 
1892. DAS AETHERISCHE OEL DER KUECHENZWIE- 
bel (Allium cepa L.). Arch. Pharm. 230: 
443-448. 
(5) Walker, J. C. 
1919. ONION DISEASES AND THEIR CONTROL. 
U. S. Dept. Agr. Farmers* Bui. 1060, 28 p.. 
illus. Revised, 1922. 
1921. onion smudge. Jour. Agr. Research 20: 
685-722, illus. 
1923. DISEASE RESISTANCE TO ONION SMUDGE. 
Jour. Agr. Research 24: 1019-1040, illus. 
(8) -and Tims, E. C. 
1924. A FUSARIUM BULB ROT OF ONION AND THE 
RELATION OF ENVIRONMENT TO ITS DEVELOP¬ 
MENT. Jour. Agr. Research 28: 683-694, illus. 
(9) -and Lindgren, C. C. 
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