Apr. 1 ,1923 Influence of Soil Temperature on Fusarium in Cabbage 85 
grown at 17° and at 29° C. This variation occurs not only with seed¬ 
lings of the susceptible strain but also with those of the Wisconsin 
Hollander. 
(20) Tlie great difference in the individuality of plants, as shown 
by the variation in the length of incubation period of the disease and 
degree of infection of plants, is conclusive evidence of a variation in 
degree of resistance. This variation in degree of resistance is, no doubt, 
due to a lack of factors or to a heterozygous condition of some of the 
plants for the factors for resistance. 
(21) The degree of resistance shown by a strain of cabbage depends 
to a considerable extent upon the environmental conditions under 
which the plants are grown. In our trials all plants remained healthy 
in ‘"sick” soil below 17° C.; many were resistant at 17° to 23°, and a 
small number were resistant at the higher temperatures. At all temper¬ 
atures within the infection range some plants showed intermediate 
degrees of resistance, whereas others were entirely susceptible. Some¬ 
what similar results were obtained with different percentages of soil 
moisture. 
(22) Fusarium resistance in cabbage becomes more pronounced 
with increasing age of the plant. Young seedlings of the resistant 
strain, Wisconsin Hollander, developed a relatively high.percentage of 
yellows when started in “sick'' soil at high temperatures, whereas 
plants grown for 30 days or more in noninfested soil, or even in “sick" 
soil below 17° C., when transferred to “sick" soil at high temperatures 
developed only a low percentage of yellows and then usually only in an 
incipient form. 
(23) This fact has practical significance in predicting, interpreting, or 
improving the performance of Siis and the other resistant Wisconsin 
strains in the following ways : 
(а) in the first place, it indicates that the strains will give the best 
results commercially when started in a noninfested seed bed during cool 
spring weather. This accords with the best practice of commercial 
cabbage growers in the Northern States. 
(б) In the second place, it indicates that these resistant strains may 
safely be recommended for trial in Fusarium “ sick" soil in all geographic 
localities where the prevailing temperatures at the different early stages 
of development of the cabbage plants are not distinctly higher than 
those in Wisconsin. 
(c) Finally, the resistance of these Wisconsin strains may be expected 
to “break down" in some degree proportional with the elevation of 
temperature above this point. However, in the Northern States, even 
in the warmer seasons, this usually stops with the incipient stages of the 
disease and leaves the crop commercially successful. If more trying 
conditions are met with elsewhere, it seems probable that through further 
selection strains showing a correspondingly higher degree of resistance 
may be secured. 
literature cited 
(1) W. L. 
1906. THIS PHYSIOLOGY OP A SIMPLE PARASITE. Preliminary note. In Year¬ 
book Khediv. Agr. Soc. Cairo, 1905, p. 171-195, pi. 6-7. References, 
p. 194. 
(2) - 
1907. THE PHYSIOLOGY OP A SIMPLE PARASITE. PART H. PlELD NOTES, 1906. 
In Yearbook Khediv. Agr. Soe. Cairo, 1906, p. 91-99, pi. and i 
col. pi. 
