eae OB a ha 
1910] PENNINGTON—LONGITUDINAL COMPRESSION 269 
plants to stakes and suspending weights upon half of the stems. 
The plants were 22 cm. in height and 8 mm. in diameter at the 
beginning of the experiment; they increased about 140 per cent in 
height and 50 per cent in diameter during the experimental period. 
The final measurements and tests showed very little difference 
between the experimental and the control plants. 
A third series of 81 selected sunflower plants was divided into 
three sets and placed under experimental conditions. The first 
set consisted of 29 experimental plants, the second set of 29 control 
plants, and the third set of 23 control plants which were relieved 
from supporting their own weight by cords looped around the stems, 
passed over pulleys above the plants, and attached to weights, 
which were kept sufficiently heavy to counterbalance the weight 
of the stems. The plants in this series were about 38 cm. in height 
and ro mm. in diameter, and were kept under experimental con- 
ditions ten days. During that time they increased 80 per cent in 
height and 35 per cent in diameter. Weights were added daily 
until each experimental plant supported 6-7 kilos. 
The usual measurements and tests showed a very great simi- 
larity in every respect in all three sets. In no case was there a dif- 
ference of more than 6.1 per cent between the averages for any two 
sets. The relative resistance to bending was as follows: experi- 
mental plants 106.1, control plants roo, counterbalanced controls 
96.2. The relative amount of xylem was: experimental plants 
103; control plants 100; counterbalanced controls 98. 
WINDSOR BEAN (GREENHOUSE PLANTS) 
Several experiments were conducted in the greenhouse with 
the Windsor bean. Experimental plants tied to stakes and with 
the longitudinal compression localized in the lower portion, control 
plants tied to stakes, counterbalanced controls, and plants which 
grew normally, without additional weight or support, were com- 
pared with reference to strength of stem and amount of mechanical 
tissue. In no case did additional weight or decreased weight seem 
to have any influence upon the plants. Stems of plants which 
had been tied to stakes were found to be slightly weaker than 
stems which had not been tied. 
