GROWING BACTERIOLOGICALLY STERILE POTATO PLANTS 
B 
it for 1 inch. The crown of the cover rose above the shoulder 1 inch. 
In their original state they were provided with substantial handles 
riveted in the center. 
The completed cover is illustrated diagrammatically in Fig- 
ure 1. 
The middle part of the handle was cut off, leaving the two up- 
right ends, 13/2 inches long, in each end of which a small hole was 
made. In the very center of the cover, a hole l^g- inches in diameter 
was made. On an axis at right angles to the axis of the original 
handle, and on a center 634 inches from the center of the cover, a 
hole V/2 inches in diameter was made. In this hole was soldered 
a brass tube 2 inches long, extending an equal distance above 
and below the cover. On the opposite side of the center an irreg- 
ularly shaped hexag- 
onal opening was cut, 
two sides being on 
radii at right angles 
to each other from the 
center of the cover, 
beginning 2% inches 
from the center and 
extending for 23^ A — 
inches, at which points 
two other sides began, 
at right angles to the 
sides formed along the 
radii and extending for 
2 inches. The other 
two sides were parallel, 
the center of the near- 
est being 1% inches 
from the center of the 
cover, the side being 
33^ inches long and 
the center of the oppo- 
site side being 4J^ 
incnes irom tne Center fig. 1.— Diagrammatic representation of the surface view, and cross 
nf tViA ociwr tVna aide* section on the line A-B, of a can cover. The irregular hexagonal 
ui ^ me lu v vi , w-ua kiue openmg> the hole at the center, and the water pipe inserted in the 
being 4 Yg- incnes long. brass tube are all centered on the line A-B. The upright ends of the 
As these cuts were made remnants of the handle are shown in the cross section 
with a chisel, accuracy in every cover was not easy and some slight 
deviations resulted. The pieces of metal which were cut out were 
reshaped, the edges brushed with a file and refitted to the hole. A 
lip three-sixteenths inch wide was soldered underneath for the cover 
to rest upon. An identification number was stamped on each cover 
and inset piece. 
In the brass tube soldered in the round hole made in one edge, a 
%-inch pipe, deeply threaded at one end, was set in plaster of Paris. 
The inside of the ends of the pipe were carefully reamed to remove 
any roughness or constriction. The pipe extended through the tube 
to the plane of the edge of the cover. After the plaster of Paris was 
well dried it was sealed with a stiff sealing wax. 
Figure 1 shows the openings and their arrangement on the cover, 
all openings being arranged symmetrically on the line A-B. A 
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