640 
Journal of Agricultural Research 
Vol. XI, No. 13 
period. The only cases observed where the heads were destroyed have 
occurred when the flag leaf and its sheath were badly attacked while the 
head was still inclosed. The bacterial exudate may then so seal the 
developing sheath that the normal escape of the head is impossible and 
these culms can not “head out” (PL 49, A). 
As to the overwintering of the organism, evidence has been obtained 
in two ways: First, blighted leaves showing the well-developed trans¬ 
lucent lesions, which had lain in the laboratory as dry herbarium speci¬ 
mens for eight months (July-March), \vere used as material from which 
to make poured-plate isolations. From these the characteristic organism 
was secured, its identity determined by cultural characters and its patho¬ 
genicity by inoculations on young barley leaves. Apparently the organ¬ 
ism lives longer in the interior of these desiccated leaves than it does in 
the dried exudate upon the surface, since poured plates from the exudate 
granules from similarly stored leaves failed to show the organism. Only 
the smaller granules were available for such trial, and further tests may 
show that in the larger exudate granules the organism may persist longer. 
The second and more direct evidence relates to the persistence of the 
organism with the seed grains which may be stored over the winter or 
disseminated widely. Field evidence indicated early that in certain 
cases the disease was introduced with seed from certain western sources. 
In following up this matter seed was collected in the summer of 1914 
from a field of Beldi barley in Montana severely attacked by the blight. 
Lesions were evident on the glumes of these plants before maturity and 
showed, although less clearly, upon the ripe grain. 
Some of this seed was planted in the trial grounds at Madison in the 
spring of 1915. The bacterial-blight was detected on the leaves in this 
plot when the plants were 8 inches high, scattered infections then oc¬ 
curring throughout the plot. At the same time no disease could be detected 
on the other barley plots in series which were planted with Wisconsin- 
grown seed supposed to be free from the disease. Later in the summer, 
however, the blight was produced by inoculation upon certain of these 
others, indicating that the difference was not primarily in varietal sus¬ 
ceptibility. 
As previously reported (5), isolation cultures were made in July, 1916, 
from the glumes of some of this same infected grain, which was collected 
in Montana in 1914. The characteristic barley-blight organism was 
found to be present, was secured in pure culture, and its continued patho¬ 
genicity was proved by inoculation experiments (Pi. 49, B). It is thus 
apparent that the organism may persist with the stored grain and remain 
pathogenic after at least two years of dormancy. 
The conclusion that the disease is introduced with the seed seems 
further justified by the writers’ observations in preceding years. Thus, 
in 1912, it first appeared in a plot of Chevalier, a two-row barley, the 
seed of which was brought from Montana. Later it developed on the 
