60 
Research Bulletin A o. 1 
place in the laboratory in another experiment. Potato tubers 
had been sterilized with corrosive sublimate solution and then 
cut into slices and put into sterile petri dishes. Some of the 
fungus was inoculated into these sections in December just 
before the Christmas holidays. One of these sections was the 
bud end of the tuber and the fungus was placed near the terminal 
bud. These cultures were neglected for several weeks during the 
holidays and when the researches were again resumed it was 
found that one of the young shoots that had developed had been 
overrun by the Fusarium, and the death of the shoot was attri- 
buted to the fungus. Later on, a section of one of these slices 
was used in some inoculation experiments with plants which were 
covered with bell jars after the pieces had been placed in contact 
with the stem. The soil and pot had been sterilized, and much 
to our surprise a luxuriant growth of Rhizoctonia developed in a 
few days. This showed clearly that the washing of the tuber 
had not killed all of the organisms in or on the skin of the tuber 
and reopened the other observations, made on the other slices of 
the same potato, for further consideration. It is very possible 
that Rhizoctonia developed during the holidays and killed the 
shoot, which was subsequently invaded by Fusarium. Other 
experiments that have been performed with pure cultures and 
sterilized soil have all been negative in result and therefore this 
single instance of an apparent infection must be accepted with 
due reserve. 
If this fungus is responsible for the wilt of potato vines at 
all, it must get into the young underground stems and roots. 
Manns reports successful inoculations by wounding roots in the 
presence of the fungus and by growing the potatoes in "sick soil," 
and says: "The disease came on much more definitely under the 
sick soil infection than it did where pure artificial cultures were 
used without incisions or root injury. The great difference 
between sick soil infection and that from pure cultures or even 
internal seed infection is that in the use of sick soil the roots 
are attacked at practically every point, while with pure cultures, 
or seed internally infected, the fungus attacks only in close 
proximity to the main root, while most of the secondary roots 
and the roots and the root hairs remain healthy." 
Data from such experiments must, at the best, be very un- 
reliable. "Sick soil," selected at random, may contain a multi- 
tude of fungi other than the particular fungus in question. The 
only reliable way of getting sick soil is to thoroly sterilize the 
soil and then inoculate it with pure cultures of the organism in 
question. Rhizoctonia solani is reported as an active damping 
off agent and it may have caused the attacks which are referred 
