300 CHAP. XXVII. ANAESTHETICS AND GEOTROPISM 



arrested. This arrest was not permanent, for introduction 

 of fresh air was found to bring about the subsequent renewal 

 of the geotropic up-movement. 



Experiment 164. Response of spring-specimen. — The 

 record (fig. 177) shows that the latent period is relatively 



Fig. 176. 



Fig. 177. 



Fig. 1 76. Effect of CO2 on geotropic response of winter-specimen 

 of Tropaeolum. CO2 applied at thick dot induced preliminary 

 enhancement followed by arrest. 



Successive dot-intervals 3 minutes. 



Fig. 1 77. Effect of CO2 on geotropic response of spring-specimen 

 of Tropaeolum. CO2 applied at thick dot and fresh air 

 substituted at circle. The effect induced is a preliminary 

 enhancement followed by a reversal. Substitution of fresh 

 air renewed normal geotropic reaction. 



short ; the erect curve, moreover, demonstrates greater 

 geotropic sensibility of the spring-specimen. After the 

 attainment of a uniform erectile movement, carbonic acid 

 gas was introduced into the plant-chamber ; this induced 

 a great enhancement of geotropic movement in the course 

 of 3 minutes, a result characteristic of the first stage. The 

 erectile movement was temporarily arrested in the course 

 of 12 minutes. There then followed the reversal of the 



