DEVELOPMENT OF WTLT-KESISTANT TOMATOES. 5 
best commercial varieties in quality of fruit were discarded without 
regard to other qualities. The most promising strains remaining were 
tested in subsequent years by repeated plantings on wilt-infested 
land beside the best commercial varieties, beside the most wilt-resist- 
ant varieties, and beside the best strains previously obtained by this 
method. 
As it is difficult to determine accurately the degree of infection 
in wilted plants, the writer has graded the resistance of strains by 
a combination of characters correlated with the degree of infection, 
viz, the percentage of infected plants, the percentage of dead plants, 
and the yield of fruit. 
The percentage of infected plants is correlated with the degree 
of infection in highly resistant material and is therefore useful in 
determining resistance when no plants die and when marked fluc- 
tuations in yields occur from variations in the environment. 
The percentage of dead plants is useful in making selections from 
very susceptible material in which all or nearly all plants become 
infected and varying percentages die. 
The yield of fruit is inversely correlated with the degree of in- 
fection in both resistant and susceptible varieties or strains. It is 
therefore useful in making selections for wilt resistance, but its 
exclusive use for this purpose is likely to lead to erroneous con- 
clusions, as yields are often affected by other factors than wilt, and 
early susceptible varieties, such as Earliana and Texas Bell, partially 
freed from the effects of the disease because of the low soil tempera- 
ture in the early part of the season, not infrequently produce a large 
part of their crop before they are killed by wilt. 
Yields in these preliminarj' tests were not determined from actual 
weights of fruit but from general appearences ; in fact, the differences 
were great enough to be easily distinguishable without the use of 
weights. 
When the three characters, percentages of infected plants, per- 
centage of dead plants, and yield of fruit, are judiciously used they 
furnish a fairly effective and rapid means of determining resistance. 
VARIETAL RESISTANCE. 
The only naturally wilt-resistant varieties of tomatoes having fruit 
of fair size and quality found by the writer are the Duke of York 
and the Buckeye State. In type of fruit and vine and in resistance 
to wilt they appear to be one variety under two names. Livingston's 
Globe possesses some resistance, enough, in fact, to be of economic 
importance, but it is not so resistant as the varieties just mentioned. 
Although the Duke of York and the Buckeye State produce large 
fruit it is rather hard, especially at the stem end, and has a large 
