4 8 4 



PLANT RESPONSE 



that this induces a very great contraction, and that in the 

 course of seven minutes there occurs an arrest of growth, in 

 a contracted position. It will also be seen that the specimen, 



after the application, actually be- 

 came shorter than it had been 

 before. The alkali therefore had 

 the effect not merely of arresting 

 growth, but also of causing an 

 active contraction of the tissue. 



Antagonistic action of alkalis 

 and acids. — We saw that in the 

 autonomous responses of Des- 

 modium and cardiac muscle, the 

 state of standstill induced by the 

 action of either acid or alkali was 

 neutralised and counteracted by the 

 antagonistic action of the other (cf. 

 fig- 1 5 5)- I have detected precisely 

 the same peculiarity in the case of 

 growth-response also. It was seen 

 in the course of the last experiment that growth was brought 

 to a state of standstill, in the contracted position, by the action 



Fig. 198. Unbalanced Record 

 showing the Action of Al- 

 kali, and the Antagonistic 

 Action of Subsequent Appli- 

 cation of Acid 



The downward arrow ( I ) indi- 

 cates application of alkali, 

 which induces arrest of 

 growth in contracted posi- 

 tion. The upward arrow ( t ) 

 indicates application of acid, 

 which by its antagonistic 

 action renews growth. . 



Fig. 199. Effect of Strong Solution of NaCl on Rate of Growth, as 

 Modified by Different Constitutions of Specimens 



At a temperature of 30 C. there is an immediate depression. Near the 

 optimum there is a well-marked resistance, and preliminary acceleration 

 before depression sets in. The same is true to a less extent at 37 C. 

 These records were taken under balanced conditions. At 44° C. there 

 was normally no growth, but this was temporarily initiated under the 

 action of strong NaCl solution. Record taken by Method of Balance. 



of alkali (fig. 198). At this point, as marked by the upward 

 arrow (f), acid was applied. This reagent now had the effect 



