48 Nebraska Agricultural Exp. Station, Research Bui. 6. 
sunk in a depression so that a truck running back and forth con- 
nected on a level with the three main tracks. A platform scale 
graduated to one-hundredth of a pound was located permanently 
at the end of the middle track. (Fig. 5.) When about to be 
weighed, the potometers on the middle track would first be 
rolled individually upon the scale, weighed, rolled upon the 
switching truck, and moved back upon the empty receiving 
track. The potometers in the second row were then switched 
back upon the middle track and weighed while passing over the 
scale. This arrangement for weighing and switching the potom- 
eters is much better than that described in the Twenty-fourth 
Annual Report of this Station. It is a great advantage to have 
the scale permanently located. 
Fig. 6.— Potometer with subirrigation-watering device for maintaining a con- 
stant moisture supply. 
POTOMETER WITH SUBIRRIGATION-WATERING DEVICE.* 
In experiments where soil moisture is not a variable factor 
under investigation and the object is to determine the total 
amount of water transpired during the growth of the plant, the 
watering device shown in Figure 6 is very simple in operation 
and is very satisfactory. 
Except in experiments to determine the effect of the amount of 
soil, the potometers were of the same size as those just described, 
16 by 36 inches, and were made in the same manner. Weighed 
1 This type of potometer was first used and described by Montgomery 
(1911). 
