1284 



LIE*E MOV^mSnTS In PLANTS* 



only the positive impulse ; strong or long continued sti- 

 mulation will transmit both positive and negative impulees, 

 the positive preceding the negative. The transmitted posi- 

 tive gives rise to increase of turgor, expansion, and accelera- 

 tion of rate of growth ; the negative induces the opposite 

 reaction of diminution of turgor, of contraction, and of 

 retardation of rate of growth. Transverse transmission is 

 only a particular instance of transmission in general ; 

 the only difference is that the conducting power for 

 excitation is very much less in the transverse than in 

 the longitudinal direction. Owing to feeble transverse 

 conductivity, the transmitted impulse to the distal side 

 often remains positive ; it is only under strong or conti- 

 nued stimulation that the excitatory negative reaches the 

 distal side and neutralises or reverses the previous positive 

 reaction. If the distal is the more excitable side, the 

 reversed response will appear as pronounced negative. 

 I give a table which will clearly exhibit the effects 

 of stimulus on the proximal and distal sides of the 

 responding organ. 



TABLK XXIV. — SHOWING RESPONSIVE EFFECTS COMMON TO PULVINI AND 

 GROWING ORGANS UNDER UNILATERAL STIMULATION. 



Effect of direct stimulation on Effect of ii.direct stinuilatioii on 



proximal side. i distal side. 



Diminution of tiu-gor 

 Galvanometric negativity 

 Contraction and concavity 



Increase of turgor. 

 Galvanometric positivity. 

 Expansion and convexity, 



When stimulus is stroug or long continued, the true excitatory effect is 

 conducted to the distal side, neutralising or reversing the first response. 



