462 BOTANICAL GAZETTE [JUNE 
With but one exception (H¢), these results show uniformly a 
decided increase in breaking strength of those under tension. The 
exceptional breaking strength of this tendril is partly accounted 
for by the fact that the break occurred in the basal third, which has 
a greater development of mechanical tissues. We can only con- 
clude from these results that tension does produce greater strength 
of tissues in the middle third of the tendril. 
3. Basal third—The next experiments were for the purpose of 
determining the effect of tension on the less sensitive basal or 
proximal third of the tendril by the same 
method, only one ligature being used on the 
one under tension, however (fig. 2), and a 
counter-weight (cw) used in the one tension- 
free, instead of the cord being tied back to 
the stem. Breaking strengths of the basal 
third in the two sets of the tendrils are given 
in table IV. 
These results show no decided difference 
in strength between the two sets of tendrils 
compared as in the preceding experiments on 
the middle third. However, it is quite pos- 
sible that the increase in strength of the 
“tension-free”’ tendrils in this experiment 
compared to the last’is due to the tension 
stimulus received by the portion between the 
two ligatures, this stimulus being conducted 
through the tissues to the basal part; the 
Fic. 2—A, tension- contact stimulus is also greater here, due to 
tendril; B, tension-free the fwo ligatures compared to one in the 
tendril; p, pulleys; 4, tension tendril.? 
ligatures; w, weights; . : 
cw, counter-weight. In order to eliminate these additional 
stimuli the following method of experimenta- 
tion was devised. Two loops of cord were made about the tendril 
not under tension at the same distance from the base as was the 
~~ 
2 A study of sections of these tendrils (see below, under anatomical study) shows 
that these stimuli causing the formation of more mechanical tissue are actually trans- 
ferred in the manner here stated. 
