THE ANGLE OF DEVIATION FROM THE NORMAL 
VERTICAL POSITION AT WHICH STEMS 
SHOW THE STRONGEST GEOTROPIC 
RESPONSE.! 
JULIA ANNA HAYNES. 
INTRODUCTION. 
SACHS (’82) seems to have been the earliest botanist to pay 
particular attention to the relation between the angle of devia- 
tion in orthotropic plant organs and the strength of the geo- 
tropic response. He found, by experiment, that main roots of 
beans and oak seedlings inclined 8 or 10 degrees from the verti- 
cal, slowly or never came into the normal position, while if placed 
at an angle of 80 or 9o degrees, the growing parts curved 80 
or 90 degrees in a few hours. In his “Lectures on the Physi- 
ology of Plants,” Sachs (87) also speaks of using in these 
experiments, thick, rigid, long internodes of such flower-stalks 
as attain considerable heights in short periods. The results led 
him to the conclusion that zones of similar developmental stages 
make various curvatures during the same time if they form 
various angles with the vertical. That is, the curvature is 
stronger, the more nearly the angle of deviation approaches to 
a right angle. If, therefore, this angle of deviation is a right 
angle, the maximum of growth-difference between the upper and 
lower sides is attained (Sachs, '74). 
Miss Bateson and Francis Darwin (88) used decapitated 
flower-stalks of Plantago lanceolata and Brassica. oleracca and 
found, after numerous experiments, that in both Plantago and 
Brassica, the greatest curvature was made by the stems placed 
horizontally, less curvature by those inclined more than 90 
No gontributions from the Botanical Laboratory of the University of Michigan. 
o. 5. 
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