EFFECT OF ASCENT OF SAP 387 



torsion. This culminated, in the course of half an hour, 

 in an actual reversal to negative or clockwise torsion of 

 — 25 mm. per 5 minutes. 



I next studied the effect of application of warm water 

 to the cut end of the stem. The resulting increased rate 

 of ascent of sap converted the negative — 25 to positive 20, 

 which is greater than the original rate. Water was with- 

 drawn once again, and the torsion became reversed to — 5. 

 Warm instead of tepid water was next applied at the cut 

 end, with the result that the negative became replaced by 

 an enhanced positive of 50. The above is typical of 

 numerous experiments. 



Experiment 206. Effect of plasmolytic withdrawal of 

 water. — Artificial drought was produced by the application 

 of a plasmolytic solution of KNO3 at the cut end of the 

 stem. The normal rate in a specimen of Phaseolus was 

 + 14 ; application of KNO3 solution at the cut end caused 

 a reversal to — 6 in the course of half an hour. 



The effect of variation in the rate of ascent of sap on 

 torsional response will now be related with the effect induced 

 in growth itself. I have already shown (p. 53) that normal 

 growth is accelerated by enhancement of turgor caused 

 by increased rate of ascent of sap, drought producing 

 the opposite effect. The relation between changes in the 

 rate of growth and of torsion will be seen by comparison of 

 the two following tables : 



Table XL.— -Effect of Alter- 

 nate Variation of Turgor 

 ON Longitudinal Growth 

 (Zephyranthes). 



Table XLI. — Effect of Alter- 

 nate Variation of Turgor 

 ON Torsional Growth 

 .'Phaseolus). 



