64 
Research Bulletin No. 1 
The data in the above table are of considerable interest since 
they so clearly show that the dry rot here described cannot be 
communicated to the underground parts of the potato plant. In 
the hills in which a badly rotted piece of potato was placed at 
planting time, as many marketable tubers were produced as in 
the hills without any such treatment. In fact no dry rot appeared 
on any of these tubers at harvest time whether dry rot pieces 
were planted in the hill or not. The planting of tubers affected 
with stem end rot* with the seed piece in each hill of plots B 
and 0 apparently did not at all increase the percentage of tubers 
affected with stem end rot or bundle blackening. Previous 
treatment of the seed potatoes with formalin and subsequent 
spraying with Bordeaux mixture had no apparent effect upon 
the crop either as to the total yield or as to the percentage of 
marketable potatoes. 
Moreover, during the seasons of 1909 and 1910 thoro search 
was made for dry rot on the new tubers. These observations 
covered ten fields containing a total of about five hundred acres. 
Not a single affected tuber was found during the summer. 
Plants and new tubers were secured from various fields during 
the summer of 1909 and a total of seven hundred and twenty 
isolations made from tubers and stems but the dry rot fungus 
was not secured. In one field, however, on August 26, dead 
potato stalks were found which were entirely rotted and crumbled 
when disturbed. From these stalks cultures of the fungus were 
obtained, together with bacteria. "During the summer of 1910 in 
only one field were the plants found to be infected. The organism 
seems to exist merely as a saprophyte in the field and does not 
attack the tubers until they are harvested. 
NATURAL INFECTION WITH DRY ROT. 
Potatoes grown in western Nebraska were planted March 1, 
1909, in the open bench of the greenhouse. These tubers were 
quite badly infected with dry rot, but to make certain, thoro 
infection of the soil, pieces of the rotted tissue were scattered 
thru the soil with the "seed" pieces. These plants made a good 
growth and remained green and healthy for twelve weeks. The 
* The "stem-end" rot here referred to includes the symptoms of vascu- 
lar discoloration described and illustrated by Smith and Swingle 1904 and 
assumed by them and many others to be caused by Fusarium oxysporum 
(p. 67). During the course of these investigations numerous isolations 
were made in various ways from a large number of tubers which showed 
clearly that, when present at all, the Fusarium hyphae were invading dis- 
eased tissues. It was found that in many cases saprophytic fungi and 
bacteria can invade this diseased tissue as readily and frequently as does 
Fusarium. 
