1028 
Journal of Agricultural Research 
Vol. XXIV, No. la 
from a hot water extract of colored onion scales, but they did not state 
the variety or color of onion used. Perkin and Everest (15, p, 201) state 
that attempts to isolate a quercetin glucoside from onion skins have 
hitherto failed. Our work shows that quercetin exists to a considerable 
extent in both the yellow and the red scales, and in the last case it evi¬ 
dently occurs along with an anthocyan. Beyond the work of Perkin, 
just cited, there is no information available as to the exact nature in 
which the red and yellow pigments exist in the onion tissue. In connec¬ 
tion with the present problem this question is now being investigated in 
cooperation with the Department of Pharmacy, University of Wisconsin, 
and results with their bearing upon the relation between parasite and 
host will be published later. It is a matter of common observation that 
upon death of the cell, the cell sap pigments readily diffuse out. Likewise 
in the onion, there is considerable diffusion of soluble pigment from dead 
outer scales but little or none from the succulent scales. 
RKI/ATION OR ONION PIGMENTS TO THE FUNGUS 
The close correlation between presence of pigment in the outer scale of 
the onion and resistance to smudge has already been pointed out. In 
further search for the substances in the plant responsible for resistance, 
a study was made of the effect of water extracts of the dry outer scales 
upon the germination and growth of the fungus. 
It has been shown that when bits of the fleshy scale of the white or 
colored onion were placed in drops of water containing spores of Colie- 
totrichum circinans, germination was^ entirely inhibited. Similar trials 
made with outer dead scales of white onion yielded no inhibition, how¬ 
ever. Thus, it was evident, that a large part of the volatile oil present 
in the fleshy tissue is lost as the outer scale dries down. It is assumed, 
therefore, where dry outer scales were used that toxicity of the volatile 
oil did not enter in to any appreciable degree in the following experiments. 
METHODS 
The methods used were as follows: Drops of distilled water containing 
spores of the fungus were placed on clean glass slides, two drops on each 
slide. Petri dishes lined with moistened filter paper were used as moist 
chambers; two slides were placed in each Petri dish, one serving as a 
control, the other as a means of testing the effect of scale extract on 
spore germination. In the drops on the latter slide bits of onion scale 
about 2 mm. square were placed, usually two such pieces per drop. 
Observations were made and recorded after 18 to 24 hours. 
EFFECT UPON SPORE GERMINATION 
Further experiments, conducted with bits of tissue from the dead 
outer scales, resulted in quite a different reaction on the part of the 
fungus than had hitherto been noted. No indication of the injury to 
control drops so evident in the last experiment was noted, showing that 
the fungicidal effect of the volatile oil is largely, if not entirely, absent 
in the dry outer scales. In the case of drops of spore suspension con¬ 
taining bits of the dry white scale, germination occurred and appres- 
soria formed as usual. The behavior of the organism was thus very 
