GROWING BACTERIOLOGICALLY STERILE POTATO PLANTS 21 
grown with their roots in sterile soil and the stems and foliage in ster- 
ile air. The ultimate object, to add to the known facts regarding the 
pathology of Fusarium on potato plants, was not achieved. The 
plants obtained were abnormal, feeble, and lacking in character, so 
as to be unfit for use as experimental host material. 
DISCUSSION 
Of the many factors which contributed to the enfeebled condition 
of the plants produced in the experiments discussed in this article, 
no single one can be regarded as primary. The principal obstacles 
appear to have been the weakened and devitalized seed, the poison- 
ous soil, the extremely artificial and unfavorable environment, and 
the ever-present menace of contamination combated only by drastic 
means. The potato is a particularly difficult plant to use in such an 
experiment. If a true seed could have been employed to start the 
plants, the experimental labor would have been greatly reduced. 
The lack of uniformity in potato seedlings and the usual weakness 
of such plants make them unsuited for experimental use in inocula- 
tion tests. A growing season long enough to give time for the plants 
from devitalized seed to recuperate and a regulated temperature 
could both be attained by artificial means, but there are other environ- 
mental factors which are less readily altered and controlled and which 
are imperfectly understood. The chemical and physical changes 
in soil which result from steam sterilization at high pressure mate- 
rially influence fertility, even when every opportunity is offered for 
the reestablishment of a normal soil flora and fauna. 
The technique employed in this work maintained a sterile soil 
throughout the experimental period and permitted the addition of 
water as needed without contamination. The methods used might 
be applicable in a number of experimental problems. 
CONCLUSION 
A method is described whereby bacteriologically sterile potato plants 
grown from vegetative cuttings or tubers may be developed under 
sterile conditions. 
