RESPONSIVE CURVATURES— NEGATIVE (lEOTROPISM 5 II 



It has generally been supposed that the active factor in 

 apogeotropic curvature was the accelerated rate of growth on 

 the convex side of the organ ; but it has here been shown 

 by crucial experiments on the unilateral application of cold, 

 that the active factor is really the responsive contraction 

 and retardation of growth on the concave side. 



