Feb. 3, 1923 
Bacterial Leaf spot of Geranium 
363 
used for his cultural tests. He states that he isolated an organism from 
both Erodium and Pelargonium and that he was convinced that the 
organism from the wild Erodium and the cultivated species of geranium 
(Pelargonium) were one and the same. He found that both strains 
cross-inoculated readily but does not mention making any comparative 
cultural tests of the two strains. In all probability he used one strain 
only for his cultural tests. 
The comparisons in this paper were started with the idea of finding 
enough agreement in the cultural tests to establish the identity of our 
organism as Bacterium erodii , and with that in view we cast about for 
explanations to account for the differences. One striking difference 
between the Texas and Maryland organisms is in the production by the 
Texas organism of a green fluorescence in beef agar, beef bouillon, 
sterile milk, and various other media. Very careful observations were 
made, but no trace of green fluorescence could be detected at any time 
in the tests with the Maryland or New Jersey isolations. The continued 
comparisons in this paper were made with the New Jersey isolation. 
Morphologically the Texas and New Jersey organisms are much alike 
and in some of the cultural tests are identical. Although in two to five 
days we have never obtained leaf-spots such as Lewis figures the two 
organisms produce somewhat the same type of disease on geranium 
leaves apparently under the same conditions, yet if they are the same 
organism why does one produce green pigment and the other not ? 
Thinking the green color might have formed through some particular 
property of the medium, two lots of peptone-beef bouillon (beef infusion) 
were made in which Witte’s and Difco peptone were used as well as two 
lots of beef extract media with the two kinds of peptone. Our organism 
acted the same in all in respect to color—there was not a trace of 
greening. Then Mr. Lewis’s platings from diseased material were con¬ 
sidered. At the start an organism appeared on his plates which greened 
the agar. Subcultures from these colonies picked from the plate produced 
the disease. Could this pigment formation be the individuality of a 
strain? If so, it is a striking variation and a feature that must be 
reckoned with when comparing strains and varieties in proving up a new 
organism. 
The New Jersey strain of the geranium leaf spot disease was used for 
the tests described hereafter in this paper. To facilitate comparison 
with Bacterium erodii the same order is followed here as in the article 
by Lewis describing that organism. 7 No work was done with Bacterium 
erodii itself, as we had no culture of that organism nor were we able to 
obtain Texas material for our own isolations. The comparisons, there¬ 
fore, were all made with the rather full tests published by Mr. Lewis in 
the article just cited. 
cultural characteristics of the organism from the dis¬ 
trict OF COLUMBIA, MARYLAND, AND NEW JERSEY 
Agar plates. —On beef infusion peptone agar +16.5 plating from a 
2-day-old bouillon culture, colonies do not appear until the third day. 
In reflected light they are cream color, shining, round with a smooth 
surface. In transmitted light under a hand lens they are a cream color 
in the center and bluish outside of center. There are delicate reticulate 
* Lewis, I. M. op. cit. 
