2 BULLETIN 1015, U. S. DEPARTMENT OF AGRICULTURE. 
-Plate I, figure 2. Not infrequently whole fields of plants wilt in 
this manner (PL II, fig. 1) and finally succumb to the disease. 
In cross and longitudinal sections of infected stems (PL III) there 
is a dark-brown discoloration in the woody area between the pith 
and the bark, but the pith itself is usually normal. The presence 
and position of this discoloration are important diagnostic char- 
acters which help to distinguish the wilt from another similar dis- 
ease known as southern bacterial blight (bacterial wilt). 
Not only the stems and leaves but also the fruits are infected by 
wilt (PL II, fig. 2). By means of the discolored tissues infection 
can be traced through the fruit stems into the fruit and even to 
the seed. 
Yearly discoveries of wilt where it has never previously been 
found indicate that it is either continually spreading or is not 
infrequently present where it has never been reported. Observa- 
tions and reports show that both of these conditions obtain. 
It is probable that wilt will eventually spread over the greater 
part of the tomato-canning areas if not prevented by the use of 
resistant varieties. Although the wilt fungus may not thrive so 
well in the North as it has in the South, the fact that it is continually 
spreading in some of the more northern States, such as Xew Jersey, 
Indiana, and Ohio, and has even been found in Michigan. New York, 
and Massachusetts, shows that it is seemingly capable of thriving in 
the more important tomato-canning regions of the United States. 
Wilt is carried to some extent by the seed, but not so commonly 
as the high percentage of fruit infections in wilt-infested fields would 
seem to indicate. The fungus passes through the fibro-vascular 
bundles of the fruit to the seed and often invades the cells surround- 
ing the seed coat. Were it not for the removal of these cells through 
fermentation and washing of the seed in the seed-saving process the 
infection of plants through the seed would be much more common. 
The fungus-bearing particles separated from the seed by fermenta- 
tion frequently adhere to it, however, and thus become a source of 
infection for the plant and a means of more widespread distribu- 
tion for the fungus. Infection of plants through the seed would 
be more common if tomato seed was produced commercially in badly 
wilt-infested regions. 
The most common method of spreading wilt is through infected 
seedlings. Tomatoes are very generally grown in seed beds and are 
transplanted to the field when danger of frost is past. Not infre- 
quently the fungus occurs in the seed-bed soil in wilt-infested 
regions. As such soil is usually rich in organic matter the fungus 
multiplies rapidly and soon invades the roots of the seedlings. 
Although this causes a discoloration of the rootlets, the grower, who 
not infrequently is unfamiliar with plant diseases, usually fails to 
