286 
F. C. NEWCOMBE AND ETTA A. BOWERMAN 
At such a time the seedHngs from the confined air showed earlier 
exhaustion by falHng over. 
All species grow a little faster and reach their condition of exhaus- 
tion one to two days earlier in the small chambers. Measurements 
showed the Fagopyrum and the Lupinus attaining a slightly greater 
height in the current of air, while Zea, Raphanus, and Pisum grew 
higher under the bell jars. Only the Zea and Pisum produce, in the 
darkroom, leaves above the cotyledons. Measurements indicated 
slightly larger leaves from the quiet confined air. 
Series II. — This series of tests was made in another darkroom 
of the same size as the preceding, and bell jars and zinc cylinders 
were used as before for one set of plants. Intermingled with the 
bell jars and cylinders stood the uncovered control plants, and a 
current of air, brought in from the adjoining greenhouse by a small 
blower and returned to the greenhouse, kept a constant draft around 
all the preparations. Except for the cooling effect of the greater 
transpiration from the exposed plants and the pots, the covered and 
uncovered plants must have been at the same temperature. 
In general the seedlings used were planted in pots of earth, allowed 
to stand in the greenhouse till breaking through the ground, then 
placed under experiment in the darkroom. Some tests were made 
with seedlings which had reached a height of lo to 20 cm. in the green- 
house before being placed in the darkroom. Since these latter 
showed in no way a behavior different from that of the younger seed- 
lings, except that they did not live as long, they will not be given 
special consideration in the record. 
A very thorough test was made with Zea mais L. (yellow dent), 
of which more than 400 seedlings were used in 7 distinct trials. The 
record for one of these trials with Zea is given here as representative 
for all: 
"July 2, 191 7. 30 seedlings about 10 cm. above earth in pots placed under 
zinc cylinders. 26 similar seedlings uncovered. 
"July 9. All seedlings in each set have fallen over, none dead. Plants under 
cover, taller, thicker, and better looking than the uncovered. The 10 largest plants 
of the covered set average 47 cm. from ground to tip of longest leaf; 10 largest 
uncovered plants average 39 cm. Of covered plants, 13 have 3 leaves each; of un- 
covered, 7 plants have 3 leaves each. Many roots growing up into air from earth 
in covered pots; none in uncovered pots. Temperature has varied from 20° to 25°." 
Besides the Zea of the last-described experiment, there were tested 
