RESPONSE TO WIRELESS STIMULATION 175 



As an illustration of the delicacy of this method, a 

 record is given of the effect of carbonic acid gas on 

 growth (Fig. 20). A jar is filled with this gas, and emptied 

 over the plant ; the invisible gas, on account of its heavier 

 weight, falls in a stream and surrounds the plant. The 



FIG. 20. Record showing the effect of car- 

 bonic acid gas on growth. Horizontal 

 line at the beginning indicates balanced 

 growth. Application of carbonic acid gas 

 induces enhancement of growth, shown 

 here by up -curve, followed by depression, 

 exhibited by down - curve. Successive 

 dots at intervals of ten seconds. 



record shows that this gave rise to an immediate accelera- 

 tion of growth, and this continued for two and a half 

 minutes ; this preliminary acceleration was followed by 

 retardation of growth as shown by the down curve. With 

 diluted carbonic acid, the acceleration may persist for an 

 hour or more. Thus the Balanced Crescograph not only 

 shows us the beneficial effect of an agent, but also tells us 

 the dose which prolongs the beneficial effect. 



Plants are regarded as extremely sluggish : and it is 



