PLATE 4 
Correlation of pigment with onion smudge infection and with the occurrence of the 
toxic entity. 
A. —Portion of outer scale removed at harvest time from a red onion set similar to 
that shown in Plate 2. (Enlarged X 3-) Note that heavy smudge infection occurred 
at the neck above the point where pigment developed, w^hile below that point the 
scale remained free from the disease. The scale tissue in the respective portions 
was tested for the presence of the toxic entity. Results of spore germination tests 
are shown in B and C. 
B. —Normal germination resulting w^hen bits of uncolored portion of scale from b 
in A w^ere added to a drop of distilled v/ater in which spores were suspended. 
C. —Abnormal spore germination similar to that shown in figure i, resulting when 
bits of the colored portion (c) of the same scale were placed in another drop of spore 
suspension. Note “rupturing” of germ tubes or production of short tubes of abnor¬ 
mally large diameter. 
