12 BULLETIN 828, IT. S. DEPARTMENT OF AGRICULTURE. 
April 11, 1917. Xot root pruned, but recently transplanted, and soil suspension 
poured on base of stem as well as into soil around plant; 72 plants, 61 per cent wilted. 
April 13, 1917. Not root pruned, but recently transplanted; 114 plants, 25 per 
cent wilted. 
May 27, 1917. Xot root pruned, not transplanted; 20 plants, 2 plants to a pot, 
none wilted. 
Averaging the percentages of infection for all these series of soil 
inoculations to potted plants, it is found that 17 per cent of all the 
nonroot-pruned plants became infected, as against 39 per cent of 
infection among the root-pruned plants. But most of the cucumbers 
had been recently transplanted, and where in these cases examina- 
tions were made of nonroot-pruned wilting plants, root injuries of 
some sort were usually found. In those cases where the plants had 
neither been root pruned nor recently transplanted, infections even 
in the presence of such enormous numbers of bacteria were rare. This 
evidence, together with that given in other portions of this bulletin, 
points to the conclusion that the wilt organism does not gain access 
to the uninjured roots of cucurbits and that under field conditions 
no infections at all come from the soil. 
VIABILITY OF THE WILT ORGANISM IN THE SOIL. 
In order to determine how long the wilt organism would remain 
viable in ordinary garden soil, heavy tap-water suspensions of the 
bacteria were poured on the soil in one corner of a greenhouse bed. 
Then at intervals tap-water suspensions of the upper 2 to 4 inches 
of this soil were made and sprinkled over the needle-punctured 
leaves of young potted cucumber plants. In no case did any of 
these plants contract wilt, although the control plants inoculated 
by needle punctures with the original suspensions promptly suc- 
cumbed to the disease. Details of these experiments follow: 
December 4, 1916. Eight plants were inoculated within one-half hour after pouring 
the bacterial suspension on the soil. Up to December 30 no wilt had occurred on 
any of them, although all plants inoculated with the original suspension used in 
inoculating the soil became infected. 
January 8, 1917. Within one-half hour after pouring the bacterial suspension on the 
soil the thin mud thus made was directly transferred to all the leaves of eight young 
cucumber plants and numerous needle pricks made into each leaf. At the same time 
the tips of two other young plants with several pricked leaves were inverted in some of 
the water suspension of soil and bacteria, left in it for 24 hours, and then held for obser- 
vation. Three days after the soil inoculation another thin-mud suspension from it in 
tap water was made and sprinkled over the pricked leaves of 13 young cucumber 
plants. All these plants were under observation for several weeks, but not a single 
case of wilt occurred. The control plants inoculated with the original bacterial 
suspension all wilted. 
January 18, 1917. Soil-suspension inoculations into the pricked leaves of eight 
young cucumber plants, made one-half hour after inoculating the soil, all gave nega- 
tive results. The control inoculations from the original suspension all gave positive 
results. 
