1909] BORDNER—INFLUENCE OF TRACTION ON STEMS 269 
The bast fibers were not well defined; many of them only very slightly 
thickened. It was therefore impossible to make an accurate count 
of their number. 
Experiment 12.. Rubus occidentalis, field culture—On June 25, 
1907, ten young stems were selected which in general appearance were 
equally vigorous. Tension fastenings were placed on five of these 
approximately 35°™ from the ground. The controls were left free. 
A weight of 2.25** at the beginning was increased to 4.5‘¢ on July 
6, and to o** 24 days later. The experiment ended September 3o. 
The decrease in height in the experimental plants was very marked. 
Growth in diameter was also less. The total bast and xylem areas 
were determined by method 3, giving an average increase in bast of 
13.6 percent. over the controls, buta decrease in xylem of 30 percent. 
This decrease may be partly attributed to the reduced growth in diam- 
eter of the experimental plants. 
Experiment 13. Vicia Faba, greenhouse culture.—The experi- 
mental plants were put under tension on October 24, 1907, the fasten- 
ing being placed just below the fifth node. Since Vicia Faba grows 
very rapidly, it was thought possible that it might respond to a stronger 
tension than that applied to stems of other species of like cross-section 
andage. A weight of 450%, therefore, was applied at the beginning, 
increased to goo®™ two days later, and to 13008" on November 6. 
Since illumination is greatly reduced at this time of the year and growth 
is comparatively slow, this large weight caused the stem to elongate 
More rapidly than the control. This was accompanied by diminished 
gtowth in diameter. The control plants were left free, and since 
Vicia Faba retains its orthotropic position with great difficulty, these 
grew larger in diameter and less in height. When the experiment 
ended on November 9, the breaking strength of the experimental 
Plants was less than the breaking strength of the controls. 
Experiment 14. Vicia Faba, greenhouse culture—The results 
of experiment 1 3 gave cause for this experiment, in which an effort 
was made to eliminate or at least minimize the effect of those factors 
which may have obscured the response to tension in the last eApen 
ment, if such a response did occur. For this reason, the experment 
Was carried on during the season of the year when illumination was 
much stronger and hence the chances for growth much better, all other 
