52 Nebraska Agricultural Exp. Station, Research' Bui. 6. 
Fig. 9. — A mature crop of corn grown in the potometers. Note the plastocene 
collars at the base of the plants for excluding rain. Also note the normal 
development of the plants. 
In those potometers to which a constant supply of water was 
added thru the jar at the bottom, the soil naturally contained all 
of the water it could take up by capillarity. The lower foot of 
soil contained 4 per cent more moisture based on dry soil weight 
than did the upper foot, while the middle section was inter- 
mediate. Variation in the total moisture content of the duplicate 
potometers was less than 3 per cent. So small a difference will 
not materially affect the transpiration rate when water is plentiful. 
WATER LOSS BY EVAPORATION FROM THE POTOMETERS. 
Since neither the potometers nor the water jars were sealed 
air-tight, it was to be expected that a small amount of water 
would be lost by evaporation in addition to that used by the 
plant. To determine the approximate amount of such loss, three 
uncropped potometers were tested during two years, 1913 and 
1914. The water jars were full of water thruout the season and 
consequently a maximum amount evaporated from them. 
