288 
F. C. NEWCOMBE AND ETTA A. BOWERMAN 
12 cubic meters, the air in which was constantly agitated by an electric 
fan. One box had its door ajar 5 cm., the other was tightly closed. 
The seedlings in each box numbered 60. The temperature ranged from 
23° to 25°. The test lasted for 4 days. 
During the progress of the experiment, it was necessary to water 
the plants in the open box twice. The other box was not opened 
during the 4 days, and the earth was moist at the close of the experi- 
ment. 
Except for a little more damping off in the closed box (there was 
some in the open box), no differences could be seen in the two sets of 
plants at the end of the 4 days. The general thriftiness of the seedlings 
from the closed box seemed a little greater than that of the seedlings 
from the open box. Measurements showed no difference in the 
average height of the two sets of plants. 
Series IV.— h very satisfactory series of experiments was carried 
through by employing two large wooden boxes, keeping the air stag- 
nant in one and in movement in the other, the two boxes sitting side 
by side in a quiet corner of a room with thermostatic control. Each 
box was 35x60x90 cm., was carefully lined with heavy paper to re- 
duce the exchange of air with the outside, and had a closely fitting 
cover. To secure agitation of the air in one box, a small blower was 
set outside, whose inlet and outlet were connected with apertures in 
the box by short lengths of iron pipe 10 cm. wide. It was soon found 
that the motor of the blower heated the air passing through the blower 
j° to 2° higher than the air in the other box. The difficulty was over- 
come by covering a portion of the blower pipe with absorbent paper 
and causing water to drip on the paper. After some adjustments 
had been made, the air in the tw6 boxes, as shown by inserted incu- 
bator thermometers, kept fairly well the same temperature, never 
differing in the two boxes more than 0.4° C. Temperatures during 
the experiment ranged from 18° to 21.5°. Observations were made 
every 2 or 3 days, and the tests lasted from 7 to 19 days. 
The following seedlings were tested, growing in pots of earth; the 
experiments being started as soon as the seedlings had broken through 
the ground: Zea mais everta Sturtev. 140 plants, Zea mais L. (yellow 
dent) 41, Triticum vulgare Vill. 39, Lupinus alhus L. 158, Pisum 
sativum L. 38, Lathy rus odoratus L. 120, Vicia faba M. (Windsor 
broad) 37, Ricinus communis L. 12. 
The difference in humidity in the two boxes was considerable, 
