2 BULLETIN 1465, U. S. DEPARTMENT OF AGRICULTURE 
pure culture would be free from biological complications. The symp- 
toms so produced might properly be termed "pure." To accomplish 
this would be of value in the study of many plant diseases. 
The attempt to grow sterile potato plants in sterile soil, the appa- 
ratus and methods developed to accomplish this end, and the various 
phases of the experiment and its results are described in this bulletin. 
The work was done at the Colorado Potato Experiment Station, 
Greeley, Colo., at the suggestion of H. A. Edson, of the Office of Vege- 
table and Forage Diseases. The writer acknowledges his indebted- 
ness to the several men who at various times aided with their skill, 
strength, and patience in the consummation of the work. 
THE APPARATUS 
Not all of the apparatus used in this experiment was newly 
designed. Most of it consisted of commonly available utensils or 
-apparatus altered and improved to meet these special needs. The 
equipment described by Briggs and Shantz 1 was adapted for use 
here, and where similarity of tool or method is revealed they have 
^priority to the idea. 
A first requirement was that the apparatus should be substantial 
throughout, to withstand hard and rough usage and neither break 
nor give way under ordinary stress. The cans filled with soil were 
heavy; they had to be moved, worked on, and otherwise handled 
while at a high temperature. No piece of apparatus could be tolerated 
whose failure to function resulted in physical injury to men, in time 
lost, or in the undoing of some previous act. A failure in apparatus, 
as well as in skill, might in a moment invalidate the labor of many 
previous months. To meet these requirements the apparatus was 
altered as the need became apparent. It is not intended to give a 
history of the development of the entire equipment, but only a descrip- 
tion of the things ultimately used. 
THE CANS AND THEIR COVERS 
One hundred cans were used, identical in every essential respect. 
These were small ash cans of heavy galvanized iron, corrugated 
throughout the barrel and having a heavy iron rim at the top and 
bottom. The bottom was slightly lowered in the center. There 
were two drop handles on opposite sides and two bail eyes directly 
above the handles and 4 inches from the top of the rim. Before use 
the cans were carefully inspected for breaks or weak spots in the 
galvanizing or solder, and these were repaired by soldering. The 
top joint between the iron rim and the barrel became broken easily, 
and constant care was necessary to keep these joints perfect. 
The cans were 26 inches high and 16 inches in diameter. The 
weight of water required to fill a can to the brim was 72.7 kilograms 
(160.27 pounds), indicating that the cubic content of a can was 
approximately 72,700 cubic centimeters (about 4,436 cubic inches). 
The covers fitted the cans tightly. They were molded in form, a 
narrow shoulder meeting the rim of the can, the cover lapping over 
1 Briggs, L. J., and Shantz, H. L. the water requirement of plants. 1. investigations in the 
great plains IN 1910 and 1911. U. S. Dept. Agr., Bur. Plant Indus. Bui. 284, 49 pp., illus. 1913. 
