SPOT, OR SPOT DISEASE. 163 



succeeded in protecting itself that the attention of 

 the grower is called to the injuries. Ordinarily 

 the first indication of a serious attack in a house or 

 in a field is a peculiar odor wholly indescribable, 

 but which once experienced will never be forgotten. 

 It is sickening, and can be approximated by putting 

 a lot of violet leaves in water, placing them in a 

 warm room, and allowing them to wilt. 



An examination of the leaves when this odor 

 is first noticed will reveal numerous greenish 

 water-soaked spots, varying in size from a pin 

 head to the blunt end of a lead pencil. There 

 may be only one or two such spots on a leaf; then 

 again the whole leaf and plant may be peppered. 

 This is spot, and two or three badly affected plants 

 in a house will make themselves known to the 

 trained nostrils. Early in the morning, before the 

 ventilators are raised, is the time to catch the odor, 

 or else at night, after everything has quieted 

 down. As the spots enlarge the central portion 

 retains at first a pale greenish yellow color, soon 

 becoming a pale buff, with a more or less distinct 

 margin of umber. Surrounding this is a ring re- 

 taining some of the pale yellow green, but almost 

 transparent. Immediately around this is a ring 

 of a green slightly paler than the surrounding por- 

 tion of the leaf, but appearing darker when 

 held between the observer and the light. 



Usually when the spots have reached this stage 

 the semi-transparent ring either becomes trans- 



