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1910] PENNINGTON—LONGITUDINAL COMPRESSION 267 
plants, which were divided into three equal sets: experiment plants, 
control plants, and counterbalanced plants. Each stem of counter- 
balanced plants was not only tied to prevent bending, but relieved 
from supporting the weight of the plant itself by tying a cord about 
the stem, passing it up over a pulley, and attaching a weight to the 
free end; this weight was kept practically equal to the weight 
of the plant. These plants were about 20 cm. in height and 9 mm. 
in diameter at the beginning of the experiment; during the experi- 
mental period they increased about 40 per cent in height and 22 
per cent in diameter. The growth was less in this experiment than 
in the former experiment because of more unfavorable weather 
‘conditions. The final measurements and tests showed no more 
marked differences than in other experiments. 
SUNFLOWER (GREENHOUSE PLANTS) 
From plants of the sunflower which were grown in pots in 
the greenhouse, 30 of those with straight stems of nearly uniform 
diameter were selected for experimentation. The stems for this 
experiment also were bound upon opposite sides with pieces of 
bamboo to localize the longitudinal compression in the lower 
portions. More weights were suspended upon the pieces of bamboo 
from time to time, until at the end of the experimental period of 
four weeks the experimental plants were supporting a weight of 
230 grams each. 
The stems were 3.5 mm. in diameter at the beginning and 
about 5.25 mm. at the conclusion of the experiment. Assuming 
that 100 represents the value of each measurement and test for the 
control plants, the following numbers represent the values for cor- 
tesponding measurements and tests in the experimental plants: 
height at the beginning of the experiment 99.8, at the conclusion 
97-4; diameter at the beginning 95.9, at the conclusion 98.4; 
tesistance to bending 66.7, to crushing 93.5. These numbers 
show very clearly that there was no greater increase in the experi- 
mental than in the control plants. The test for resistance to 
a bending especially showed less strength in the experimental than 
in the control plants. 
Although the mechanical tests would seem to show conclusively 
