466 
Journal of Agricultural Research 
Vol. XXVI, No. 10 
All remaining plants were washed from the soil and examined. The 
controls showed at higher temperatures a few unimportant lesions at 
the cotyledons, of a very different nature from that caused by the Fusa- 
rium. All remaining plants in the inoculated soil at and above 21 0 C. 
showed red-brown shrunken stems for a distance of from 1 cm. at 21 0 C. 
to 2 cm. at 2 7 0 C., where roots were also extensively blackened. At 
18° C. all plants were nearly or quite girdled by superficial lesions, which 
did not penetrate to the vascular bundles. At 12 0 C. small brown 
lesions were found from which the fungus was isolated. 
Since this experiment indicated clearly that soil temperature controlled 
the development of the disease, three subsequent series upon a larger 
scale were placed in the tanks for the purpose of obtaining more extended 
data. Two of these series were in soil supposed to be free from fungi 
which infect peas, but the results indicated that this was not invariably 
the case. Not only did Rhizoctonia occur, but other species of Fusa- 
rium which were shown to have almost no ability as parasites by them¬ 
selves entered the exposed vascular system of plants damaged by the 
parasitic species of Fusarium, and caused a more rapid wilting than the 
parasite alone could bring about. 
Setting aside these results which were clearly brought about by the 
accidental introduction of minor parasites, the results were in entire 
accord with the final series in which steam-sterilized soil was used. 
At each of the temperatures in this series five pots were planted with 
10 Alaska peas each. Three pots were inoculated by spraying the seed 
as planted with a suspension of spores of the same strain of this Fusarium 
that had been used in the previous series. The dates at which plants 
wilted are shown in the following table. These dates are necessarily 
somewhat irregular inasmuch as badly diseased plants will remain turgid 
for a long time during cloudy weather and succumb suddenly when sun¬ 
shine falls upon them. It will be seen from this table that while wilting 
begins at 24 0 C. almost as soon as at the higher temperatures it soon 
diminishes. This is due to the fact that the diseased plants have begun 
to send out roots from above the point of injury, so that from this time 
forth they can obtain moisture for maintenance and slow growth through 
these roots at the surface of the soil, even though the stem is completely 
rotted off below them. 
T able) IV .—Record of the dates at which pea seedlings inoculated with Fusarium martii 
var. pisi wilted at each of the soil temperatures maintained a 
• 30 Alaska peas were planted at each temperature on Jan. 6. 
