632 
Journal of Agricultural Research 
Vol. XI, No. 12 
ance. The leaf was washed carefully in sterile water, dipped into 95 
per cent alcohol for a few seconds, and rinsed well in sterile water. The 
leaf was then cut across with a sterile scalpel at the ligule where the 
midvein is thickest. This thickened portion, when cut thus, exposed 
two comparatively large, interior surfaces practically free from external 
contaminations. By gentle pressure on the midvein a small drop of 
the milky gray bacterial slime was forced from the interior to the cut 
surface. This was touched with a sterile platinum needle and agar 
strokes made. Eight such cultures were made and, within three days 
at room temperature, these gave similar growths, all apparently domi¬ 
nated by one organism. Plates poured from one of these cultures gave 
abundant colonies of one type, and several pure cultures were obtained 
from these. All proved to be the same organism with the characteristic 
cultural characters and all proved to be pathogenic when sprayed on 
young barley plants. Infections similar to the natural ones resulted in 
all cases from such inoculations, and the organism was reisolated. Con¬ 
trol plants remained healthy. 
The organism has also been obtained, although with more admixture 
of other species, by each of the following methods: 
(1) Similar surface washing and disinfection have been made of in¬ 
vaded leaf tissues. These were then cut into pieces and laid upon the 
surface of nutrient agar. Abundant bacterial growth spread promptly 
from the cut edges of such leaf sections. This proved to contain a mix¬ 
ture of species, but from it the parasitic organism has been isolated by 
making further streak and dilution cultures. 
(2) The surface exudate from diseased tissues is teeming with bac¬ 
teria. Isolations have been made from both fresh and dried exudate at 
various times. While other organisms may occur, the pathogenic species 
is readily secured from the exudate in either condition. Isolations have 
been made from fresh exudate taken directly from diseased plants in 
the field, also from such plants when the exudate has been forced out in 
the moist chamber and from plants artificially infected in the greenhouse. 
In the same way the organism has been obtained from the hardened 
granules of the exudate. In one case the granules were picked off the 
leaves, placed in sterile water blanks, in which they quickly soften and 
diffuse, and from these successful platings were made. In another case 
small exudate granules were planted directly on agar plates and the 
organism recovered from the resulting growth. 
(3) The organism has been secured also from the invaded leaf tissues 
which had been kept as dry herbarium specimens for eight months. 
Small pieces cut from the lesions were immersed directly in bouillon for 
one-half hour and platings then made from this. Pure cultures of the 
organisms were thus obtained and pathogenicity proved by inoculations. 
(4) The organism has also been isolated from old barley kernels. On 
July 18, 1916, pieces of glumes from infected barley 2 years old were 
