Dec, 17, 1917 
Bacterial-Blight of Barley 
639 
RELATIONS TO HOST TISSUE 
A study of razor sections of the lesions as they occur in fresh leaves 
show the general facts to be as follows: The bacterial invasion is in the 
parenchyma. The parenchyma cell walls become disintegrated and in 
the interior tissues long rifts result, which extend lengthwise of the leaf 
blades. In such lesions the bacterial slime fills the interior cavities, 
expelling the air; hence, the translucency of the invaded areas. Later 
this bacterial slime hardens to a resinous texture, making the translucent 
condition a permanent characteristic of the older lesions. 
For detailed histological studies material was secured from recently 
infected young barley leaves. These had been inoculated by spraying 
with a water suspension of a pure culture and showed numerous small 
translucent infection areas. Pieces of these were fixed in boiling absolute 
alcohol saturated with mercuric cholorid, embedded in paraffin, and sec¬ 
tioned. Such sections stained with carbol-fuchsin showed infections to 
be stomatal. In some cases the invasion was as yet confined to the 
stomatal chamber which might be only partially occupied or crowded 
full of the organisms. Numerous cases showed intercellular invasions in 
the parenchyma in the early development of the lesions. In other cases 
later stages were in evidence where the bacteria had developed in large 
masses, evidently spreading from the stomatal chambers through the 
intercellular spaces, crowding apart and crushing the parnchyma cells. 
Instances of advanced invasion were found where the cell walls had par¬ 
tially disappeared, but the details of wall solution have not received a 
critical study as yet. In the older lesions, as noted above, there occur¬ 
red long cavities filled with the bacterial growths. It is from such cavi¬ 
ties in the advanced stages of the lesion that the bacterial slime may be 
squeezed out which has been the source of material for the isolation and 
inoculation work previously described. 
OVERWINTERING AND DISSEMINATION 
The fact that the disease may attack the heads early in their develop¬ 
ment has already been pointed out. The glumes may show water- 
soaked areas like those on the leaves and, upon these, drops of the bac¬ 
terial exudate may appear and harden into tiny resinous granules or 
spread as a glistening film. Observation of these facts at once suggested 
two questions, each of much importance. (1) How much is the grain 
checked or injured by such attack? (2) Does the organism overwinter 
on such grains or other barley tissues ? 
As to the first, the writers' observations have failed to detect any 
case where the grains are killed, although in certain cases there may be 
considerable injury. Although they may be more or less shrunken, 
they generally mature and are viable. This seemed somewhat surprising, 
in view of the extent of the damage to the leaves, but is apparently ex¬ 
plained in part by the fact that the heads are susceptible for so brief a 
