44 
TENTH REPORT. 
THE INFLUENCE OF CONTACT AND TENSION UPON THE TEN- 
DRILS OF PASSIFLORA CAERULEA. 
W. D. Brush. 
The present paper contains a brief sketch of a part of the experimental 
work upon tendrils carried on by the writer during the past two years. This 
investigation was undertaken to determine the effect of contact and tension 
upon the strength of tendrils. Special care was taken to secure proper 
methods of comparison since the factor of individual variation must be 
taken into consideration in such work. 
Experiments were first conducted to determine the effect of contact alone 
and of tension added. From these experiments the breaking strengths 
were found to be in about the following proportions: 
Free tendrils 245 grams. 
Tendrils with contact alone 732 “ 
Tendrils with tension added (20 g.) 1031 
These results show that contact has a marked effect in producing greater 
strength in the tendril ; however, of the effect of tension we cannot tell from 
these experiments, since the increase in strength with tension may be due 
to a greater contact and pressure stimulus. 
This contact stimulus was eliminated in other experiments by applying 
tension to the tendril by means of ligatures so that in the experimental a 
certain region was under tension while in the control the corresponding 
region was not under tension while the contact was practically the same in 
each case. In these experiments an increase of nearly 50% was found in those 
under tension, showing that tension as well as contact has a marked effect 
in giving strength to the tendril. Other experiments have shown that in- 
creased contact pressure produces greater strength in the tendril, though 
increased contact through tension is found to play only a very small part- 
in giving increased strength to the tendril in nature. 
Marked anatomical differences are found in the tendril due to contact 
and to tension, but of these we will not treat in this brief summary. 
To suln up the results of this work it was found that contact has a decided 
effect upon giving strength to the tendril, and by the addition of tension 
a still greater strength is obtained — each factor having a characteristic 
effect upon the anatomical structure of the mechanical system. 
A full treatment of this work is to be published later. 
Botanical Laboratory, University of Michigan. 
