266 BOTANICAL GAZETTE [OCTOBER 
mental plants at the beginning of the experiment was gradually 
increased to goo#™ on December 20. It was the purpose of this 
experiment to determine, by prolonging the experimental period and 
growing the plants to maturity, whether the response in the earlier 
and actively growing period was continued to the end of the vegetative 
period. For this reason no additional weights were added after 
December 20. Both experimental and control plants broke with 
almost the same weight. The experimental plants were much more 
brittle and in most cases broke with a smooth, clear break, while the 
controls showed more of the elasticity and toughness which was 
characteristic of the stems in experiment 5. 
Experiment 7. Phaseolus vulgaris, greenhouse culture.—After 
finding that response to tension, if any had occurred in experiment 6, 
was vitiated by permitting the plants to grow to maturity, experiment 5 
was repeated, beginning March 5 and ending fourteen days later. The 
weights used, 2008™ at the beginning, were increased to 4508" March 
g and to 7oo®™ four days later. The experimental plants showed an 
average increase in breaking strength of 3.32*¢, or 42.5 per cent. 
The number of hard bast elements was determined by method 5. 
The experimental plants showed an average increase of 167, Or 14.9 
percent. The results of this experiment, therefore, agree with those 
of experiment 5. The tension fastening in this and also in experl- 
ment 6 was made at the same place as in experiment 5. 
Experiment 8. Vinca major, greenhouse culture.—In selecting 
plants for this experiment those were taken which had young and 
actively growing shoots, uniform in general appearance and length. 
No measurements were taken at the beginning of the experiment, 
December 1, 1906. The experimental shoots were put under a tension 
of 50®™ at the beginning, which was gradually increased to 300°" 0? 
December 21. The control plants were fastened to an upright suP- 
port, but were not under tension. tee 
The breaking strength was tested in the internode just below the 
fastening which was in an active growing condition in each plant 
when the experiment was started. The average shows an increase 
the experimental plants of 649%™, or 15.2 per cent. 
Experiment 9. Vinca major, greenhouse culture.—It was - 
purpose ofthis experiment to determine whether internodes which 
~ . pingip' te Mens Ue oT Si 
Wee SU Ss ey tr ee kere 
: 
4 
‘ 
4 
