VOLUME LIII NUMBER 6 
THE 
EHOTANICAL G4AZETTE 
JUNE 1912 
THE FORMATION OF MECHANICAL TISSUE IN THE 
TENDRILS OF PASSIFLORA CAERULEA AS INFLU- 
ENCED BY TENSION AND CONTACT 
W. D. Brus 
(WITH THREE FIGURES) 
Introduction 
The mechanical theory of growth, as put forth by SAcus (20), 
has of late years been replaced by the idea of self-regulation in the 
plant depending upon external stimulus. This idea is followed 
quite closely by Prerrer (18).t As a consequence, considerable 
attention has been directed to the effect of strain upon plant 
tissues, since by this new theory we might expect the plant to 
respond to a state of strain by a greater development of strengthen- 
ing tissues. The present investigation was undertaken to deter- 
mine if such self-regulation is present in the tendril that 
stronger mechanical tissues are produced where needed. To 
state the problem of the present paper: Do tendrils which are 
functioning to support the plant possess greater strength than 
those which have grasped no support, and if so, how is this strength 
increased, and is it due to tension or to contact, or to a combina- 
tion of both ? 
Darwin (5) observed that tendrils which have grasped no 
support soon die; Worcitzky (26, p. 39) noted a greater breaking 
strength of tendrils with a support over those without. Other- 
Wise, no attempt has been made to answer this question. 
* For a discussion of these two theories see NEWCOMBE (15). 
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