Dec. 10,1913 
Disease of Sugar-Beet and Nasturtium Leaves 
193 
REISOLATION FROM INOCULATED TISSUE 
Out of a small piece of tissue cut from one of the spots produced by 
inoculation a bacterial organism was isolated by means of agar plates, 
and by careful comparison with previous cultures was found to be 
similar in all respects to the organism obtained from the original diseased 
leaves. As soon as suitable cultures of this reisolated organism could 
be grown, inoculations were made into healthy young plants, and again 
the characteristic brown and shriveled spots were produced, with an 
abundance of active bacteria in the tissue. By these and other similar 
experiments it is proved beyond a doubt that the nasturtium leaf spot 
is caused by a bacterial organism. The manner in which the bacteria 
gain entrance to the tissue of the host has not been fully demonstrated, 
but from observations made during the investigation it seems probable 
that insect injuries, as well as mechanical wounds, open the way for the 
entering of the parasites. 
CROSS-INOCULATIONS BETWEEN HOSTS 
After proving that the right organism had been isolated from either 
host, inoculations into leaves of other plants were made, with the result 
that the sugar-beet organism proved very infectious to nasturtium, and 
likewise the nasturtium organism proved infectious to the sugar beet. 
But as the two investigators were working independently, each with 
one organism, this interesting fact had no particular significance at the 
time. Nasturtium leaves inoculated with the sugar-beet organism 
became spotted and watery-looking for some distance beyond the in¬ 
oculation pricks, appearing in all respects similar to spots produced by 
inoculations with the nasturtium organism. Later, the watery-looking 
areas turned from a yellow to a brown color, and still later these tissues 
dried up and fell out (PI. XIX, fig. 2 ). Some leaves drooped and died. 
The check leaves showed no discoloration; nor did any part of the tissue 
fall out, as in the inoculated leaves. 
Three years afterward the same strain of the organism was inoculated 
into young nasturtium leaves at the same season of the year and under 
practically the same conditions as before, but there was a slight in¬ 
fection only, though young sugar-beet leaves inoculated with the same 
culture were badly infected. 
Although inoculations with the nasturtium organism into sugar-beet 
leaves produced the disease, this strain of the organism was not so in¬ 
fectious as the sugar-beet strain on nasturtium. This difference in the 
behavior of the organisms in cross-inoculation was considered to be one 
of host influence. 
