CHAPTER VI 



LONGITUDINAL RESPONSE OF RADIAL ORGANS 



Absence of lateral response movements in radial organs due to mutually antagonistic 

 effects of equal contractions of diametrically opposite sides — Lateral response 

 in radial stem of Walnut under unilateral stimulation — Also in pistil of Musa — 

 Diffuse stimulation of radial organ causes longitudinal contraction — The 

 ' Kunchangraph ' — Longitudinal contraction of stamens of Cynerea not unique 

 — Similar longitudinal responses obtained with stems, roots, tendrils, petioles, 

 stamens, and styles of ordinary plants — Also in fungi — Responsive contrac- 

 tion in Passijlora, comparable in extent with that in Cynerea — Longitudinal 

 response in plants modified by the physiological variations due to age, season, 

 and chemical agencies. 



We have now considered the phenomenon of responsive 

 lateral curvature in plant-organs such as leaves, and have 

 seen that it is brought about by the differential contraction 

 of two unequally excited halves. But in the case of radial 

 organs, under diffuse stimulus, such responsive movements 

 are not usually noticeable, hence these organs have generally 

 been regarded as insensitive. 



It is, however, conceivable, as already said, that this 

 absence of responsive movement might be due to the occur- 

 rence of simultaneous contractions in diametrically opposite 

 sides, which would balance each other, and thus permit of no 

 lateral movement. The correctness of this supposition might 

 be tested in either of two ways. We might, for instance, 

 apply a unilateral instead of a diffuse stimulus, and so 

 brine; about a lateral contraction. Or wc might use a diffuse 

 stimulus, and look for the contraction in length of the speci- 

 men as a whole. 



Experiments showing equal and opposite reactions of 

 radial organs. — If we apply local and unilateral stimulus, 



