462 
Journal of Agricultural Research 
Vol. VIII, No. 12 
spicuous on the leaves, are usually caused by the coalescence of two or 
more separate infections which often occur in clusters when in the 
mesophyll regions and in a linear direction when along the veins, seem¬ 
ingly where the water gathers and is last to evaporate. 
The top side of the spot thus appearing becomes a reddish brown color 
over a circular area at the center and shrinks slightly in thickness. The 
colored area increases in size until it conforms to the angular shape of the 
affected part, the red advancing to the margin and the center shading 
off to gray. On the underside the spot becomes a brown color, though 
the dark green, characteristic of the young spot, remains as a narrow band 
about the margin until the latest stages of development, a place where 
the activity of the disease continues longest. When the green band 
finally disappears, the brown replaces it, giving a sharp angular margin 
to the spot. These color changes may develop quickly, so that the entire 
spot will be brown eight or nine days after inoculation; but usually they 
proceed more slowly, leaving the spot dark green for five or six days. 
seed infection 
The source of bacteria for the first infections of each season is as yet 
undetermined, because of conflicting experimental results obtained dur¬ 
ing the past summer; however, such a problem can be solved satisfactorily 
only when great numbers are used under the most favorable circum¬ 
stances. One experiment, or series of experiments, can not be expected 
to settle the matter. 
Over 2,500 seedlings from seed of various sources grown during the 
winter in all variations of temperature and moisture in the greenhouse 
and laboratory failed entirely to show the disease. Two instances of 
cotyledonary infection occurred in the late spring upon seedlings in the 
greenhouse. An acre field planted on April 20 was entirely free from 
the disease until August, except in such portion as had been used for 
inoculation experiments. Another field near by, planted partly with 
these same seeds and partly with others on May 15, developed consider¬ 
able disease in both lots of seedlings, though the season was rainy and 
the chopping was delayed; and no data as to the amount of disease due 
to the seed and that due to local dissemination could be secured. It was 
true that, of the diseased seedlings examined, equally as many had coty¬ 
ledons free from the disease (84) as had them spotted {78). 
In order to decide more carefully the probability of seed infection, 
an experiment was arranged in which samples of various lots of seeds 
were planted in plots, seven rows wide, the rows being 50 feet long and 
3 feet apart. Because of the triangular shape of the land available, 
these dimensions could not be strictly adhered to; yet each lot of seed 
was represented by one such plot at least. Most seeds used were samples 
obtained from several growers in various parts of the State, who had 
fields badly infected early in the summer, such as would likely be due to 
