eS Ye 
1909] = BORDNER—INFLUENCE OF TRACTION ON STEMS 261 
Experiment 2. Helianthus annuus, field culture. — After the 
inferior plants had been removed, those used in this experiment stood 
15 to 20°™ apart in the row. Every other plant was used as a control. 
The tension fastening was placed just below the second pair of leaves 
on the experimental plants. The control plants were left free. The 
experiment began June 21, 1907, and ended ten days later. A tension 
of 250™ was applied to the experimental plants at the beginning of 
the experiment. This was increased to 750%™ the following day and 
to 19008™ on June 25. 
Table II gives an average of the measurements and the breaking 
Strength of these plants. The average increase in breaking strength 
for the experimental plants over the controls was 2736%™ or 19.6 
per cent. 
The height measurements in this experiment confirm the work 
of ScHoitz and HEGLER (’93), showing a lessening of growth during 
the first 24 hours, followed by an increased growth for the next four 
ays. 
TABLE III.—Helianthus annuus 
Dis 
Diam. just . Just, tance | Break- 
No. of : Height to 4th above rst pair above 2d pair |of break} ing 
: Height in) eam, i f leaves above _|strength 
— pair of leeves, | of pes eee ee ae 
in cm 
Nie Eee ee i ed ew ad 
July | July | July | July | July | July | July | July | July | July 
Exp. I 30 18 18 Ric) 18 fo) 3! Pd 
Av........] 36.07] 89.6 | 32.33] 44.6 | 9.4 | 15-95] 7-58 | 13-39] 12-3 | 69-99 
Control 3 
AVeos- 5, 38.01] 90.5 | 34.6 | 45.08] 9.64 | 16.03] 7-69 | 14.37) 13-9 “12 
ee Ries ee as ee 
Experiment 3. Helianthus annuus, field culture——Much older 
and larger plants than those used in experiment 2 were put under ~ 
tension July 18, 1908. This was gradually increased from 200%" 
at the start to r950%™ on July 27. The experiment ended July 3o. 
It was the purpose in this experiment to determine whether the same 
tension would have the same influence on larger and older stems as 
On younger and less woody ones. The average increase in breaking 
Strength as shown in table III in response to a tension of practically 
T900%™ was 3.87%, while in experiment 2 the increase for a period 
Of Io days was 2. 74*s, The increase as a percentage of the average 
