392 CHAP. XXXIV. THE MECHANISM OF THE TWINING STEM 



with gas or vapour, they are blown into the cylindrical 

 chamber surrounding the plant. 



Experiment 211. Formaldehyde. — The typical action of 

 poison is exemplified by the effect of the application of 7 

 per cent, solution of formaldehyde to the cut end of the 



Fig. 221. Effects of Chloroform and Ether on autonomous 



torsion. 



The record to left shows the effect of chloroform applied at 

 arrow. There is a preliminary acceleration followed by- 

 reversal. 



The record to right shows marked acceleration under dilute 



vapour of ether. 



stem. My investigations on the effect of poison on growth 

 has shown that the preliminary effect is an enhancement of 

 growth, followed by arrest and by the death of the plant, often 

 signalised by a spasmodic contraction (p. 46). In the case 

 of the twisting growing stem, the automatic record (fig. 220) 

 shows the different phases of reaction. The immediate effect 

 of poison is an enhancement of the rate of normal torsion, 

 seen in the wider spacing of the successive dots. This 



