88 
AMERICAN JOURNAL OF BOTANY 
[Vol. io, 
Plate XI 
The Effect of Different Combinations of Soil and Air Temperatures upon the 
Tomato Wilt Disease 
“A” is air temperature; “S, M soil temperature 
All plants alike were grown for one month in uniformly inoculated soil. Each pot is 
representative of a series, the different combinations of temperature conditions being shown 
in the labels. 
Of the nine temperature combinations only two produced evident wilt symptoms, viz ., 
soil 27°, air 27°, and soil 27°, air 33 0 C. Especial attention is called to the middle plant 
in the upper row, grown in soil 27 0 , air 17 0 C. This soil temperature (27 0 ) is the optimum 
for the disease; examination showed that the Fusarium had entered the roots, yet the 
disease was so inhibited by the low air temperature (17 0 ) that the plants made a vigorous 
growth with no wilt. The plants at soil 17 0 , air 27 0 C., also deserve especial notice. 
