Relation of Nonavailable Water to Hygroscopic Coefficient 2o 
Thruont the latter portion of the experiments of 1910 and 
1911 the humidity was recorded daily at 8 a. m. and at 5 p. in., 
using a wet-bulb thermometer. The mean humidity at 5 p. m. for 
monthly decades is given in Table 3. The data for the humidity in 
the open air at the same hour are from the record of the Lincoln 
station of the United States Weather Bureau, which is only three 
miles from the Experiment Station. The differences in general 
are not great, the humidity being somewhat lower in the open air 
than in the greenhouse, notwithstanding the high temperatures 
which prevailed in the latter, due probably to the presence in the 
greenhouse of a number of pots with plants belonging to other 
experiments, to which water was applied daily. During the first 
and the last three decades in 1911 there were none of the watered 
pots in the greenhouse and during these two periods the air was 
much drier than that outside. 
In the experiments of 1910 and 1911 the daily maximum and 
minimum temperatures were recorded from the time the experi- 
ments were well started until the plants died. The daily maxima 
are shown in Table 4 and the daily means — the average of the 
maximum and the minimum — in Table 5. The thermometer was 
hung at the level of the cylinder tops in a well ventilated wooden 
shelter, placed at one end of the row of cylinders. When in 1910 
it was found that under the conditions prevailing the plants in 
moist soil apparently suffered no ill effects from temperatures up 
to 110° P., no effort was made to keep the daily maximum tem- 
perature below 105° F. As soon as the temperature reached this 
point steps were taken to prevent it rising higher. While the 
means of ventilation in the greenhouse were entirely inadequate 
to keen the maximum temperature below 100° F. on bright days, 
it could be kept below 112° F. except under very unusual condi- 
tions. The occasions in 1910 on which it rose above this were 
afternoons on which after cloudy, threatening weather the sun 
came out very bright. The ventilators having been closed to keep 
out any rain from the threatened storm and not being opened on 
the appearance of the sun. the temperature rose rapidly. For this 
reason Sundays were especially the days of high temperatures — 
as May 8 and 29 and June 12. 1910. The high temperature of 
June 12, 1910. viz, 124° F.. practically terminated the experiment 
of that year, all plants dying rapidly after this. The very high 
temperatures recorded in 1910 were usually of short duration, 
because as soon as a visit to the greenhouse showed the tempera- 
ture to be very high means were taken to quickly lower it. 
