14 Bergman.— -Relation of Aeration to Growth and Activity of 
R. sceleratus , potted in soil, were placed in vessels of water so that the 
surface of the water came above the level of the tops of the pots. Duplicate 
sets in swamp water were also set up. In two days the plants of Impatiens 
began to wilt. In three days they were badly wilted, and in four days 
were wilted beyond recovery. On the fourth or fifth day plants of Pelar- 
gonium and Phaseolus began to wilt, and if left in water two or three days 
longer the leaves turned yellow and dropped. Cyperus and Ranunculus 
showed no ill effects, but grew vigorously with their roots submerged. 
Later the same experiment was repeated, but as soon as the plants 
showed signs of wilting air or oxygen was supplied. It was found in all 
cases that the plants, if not too badly wilted, could be restored to normal 
condition and could be kept growing indefinitely if aeration were continued. 
After a week or ten days all plants developed new roots at or near the 
surface of the water, after which the plants were able to live without having 
oxygen or air artificially supplied. No difference in the behaviour of plants 
in tap-water as compared with those in swamp water could be noted. For 
this reason, and also because of the difficulty of obtaining swamp water 
during the winter months, the use of swamp water in later experiments 
was discontinued. 
Effects of excluding Air from Roots in Soil. 
Two plants of Pelargonium , potted in soil, were set up in the following 
manner. The leafy stems were passed through the mouth of a wide-mouthed 
bell-jar so that the stem and leaves came out into the air while the roots in 
the pot were under the bell-jar. The mouth around the stems and the base 
of the bell-jar were sealed with wax so as to be air-tight. Carbon dioxide 
was then passed through to replace the air. This was repeated morning 
and night to maintain an atmosphere of pure carbon dioxide. A watering 
device was so arranged that water could be added without admitting air at 
the same time. A slight wilting of one plant was apparent on the second 
day following, and on the third day the wilting was very evident. Wilting 
of the second plant did not begin until the fourth day, but on the fifth day 
it had become very pronounced. The leaves on both plants after wilting 
became yellow and soon dropped. The yellowing and dropping of leaves 
continued until the test was ended, ten days after it was begun. The soil 
was found to be normally moist at the end of the test. 
A plant of Impatiens balsamina was arranged as just described for 
Pelargonium , and the air replaced by carbon dioxide. On the second day 
the plant was slightly wilted, and on the morning of the third day badly 
wilted. The plant was removed at noon on the third day. On the follow- 
ing day the plant appeared as if badly frosted. This plant never recovered. 
