THE INFLUENCE OF TRACTION ON THE FORMA-— 
TION OF MECHANICAL TISSUE IN STEMS: 
Joun S. BoRDNER 
Introduction 
The following investigation was directed to a further knowledge 
of the influence of traction in the direction of the longitudinal axis 
on the formation of mechanical tissue in the stems of plants. 
Petioles, tendrils, and roots were not investigated, because the 
wo k of HEGLER (9), Batt (1), and Hrpparp (11) was primarily 
on stems, and it was my purpose to add further and more detailed 
experimental evidence to the work done by these investigators. 
This research was carried on in the Botanical Labo atory of the 
University of Michigan. It was under the direction of Prof. F. C. 
EWCOMBE, to whom I am indebted for encouragement and helpful 
Suggestions. I wish, also, to express my appreciation of the interest 
manifested in my work by the other members of the staff in the botani- 
cal department. 
Historical 
I. STEMS: INFLUENCE OF TRACTION 
BARANETSKY (2) observed that a stem of Gesneria tubiflora 
Weighted with 308" made less growth than one remaining free. 
ScHOLTz (26) verified this observation of BARANETSKY, and found 
that stems when subjected to traction first grew more slowly and 
later more rapidly than the control plants. This he att ibuted to a 
change in the physical condition of the cell resulting from the educed 
ydrostatic pressure. He furnished no experimental evidence to 
support his theory. HEGLER (9) produced the first experimental 
evidence to show that plants respond to tension by an increased 
formation of mechanical tissue. ‘This supported the theory which 
Was generally adhered to by plant physiologists previous to that time; 
Viz., that a plant reacts toa gradually increasing strain by an increased 
___Contribution No. 111 from the Botanical Department of the University of 
Michigan. 
E351] ! [Botanical Gazette, vol. 48 
