EFFECT OF SOIL TEMPERATURE ON BEAN PLANTS 517 
disease, but it was obvious at harvest time that the plants in two of the 
control cultures of the series of 24° were severely injured. 
In addition there were *'weak" plants in nearly every culture. 
These could not be detected as such for two weeks or more after the 
plants were up and it was then too late to correct for the trouble. In 
fact it was thought for some time that some of these plants were ones 
on which infection had been particularly severe. As there were plants 
of varying degrees of "weakness" it is not possible to throw the poor 
plants oat, of consideration. 
Furthermore, it is not possible to make a comparison between the 
cultures grown at the two temperatures because of the fact that the 
plants grown at high temperature developed more rapidly from the 
very beginning and thus matured under a different set of air condi- 
tions. In this experiment this meant that the plants grown at the 
highest temperature had very much less sunshine than those grown at 
22°. The difference is noticeable in part in the total dry weight of 
seed, but some of the difference is attributable to a more severe in- 
fection on control plants grown at the high temperature. 
Finally the difference in growth at the two different temperatures 
might have been due in part to a difference in air temperature. Ther- 
mometers suspended over the water baths at a distance of 15 cm. from 
the surface showed constantly a higher temperature over the bath at 
34° than over the ones at 22° and 15°. The difference varied from 
.5° to 4.5° and averaged from 3° to 4° higher. 
With these four considerations in mind it may now be stated that 
the average yield per plant for "healthy" plants in the series at 34° 
was 1. 45 1 grams of air-dry seed. For the infected plants the average 
was 1. 081 grams. Thus the presence of this Fusarium on the roots of 
beans under the conditions stated resulted in a direct loss of 25.5 per- 
cent. For the cultures grown with a soil temperature of 22° the aver- 
age yield per healthy plant was 2.361 grams. For the inoculated 
plants it was 1.557 grams. Here the reduction in yield on account of 
disease was 34 percent. 
The most interesting feature of the experiment is the fact that 
these beans grew faster and matured a crop earlier with the higher soil 
temperature. The relatively small difference in air temperature may 
account for some of this difference in growth but certainly cannot 
entirely account for the results obtained. Wholly aside from its scien- 
tific interest the question may have an important practical bearing for 
