SUMMARY 59 



The effect of rise of temperature to an optimum is seen 

 in the enhancement of various activities of the plant. These 

 activities decline at a temperature above the optimum. 

 There is also a minimum temperature for arrest of growth, 

 and of autonomous pulsations of the leaflet of Desmodium 

 gyrans. 



Shock-stimulus induces the D effect, shown in the fall of 

 Mimosa leaf, in the diminution of the rate of growth, and 

 in the electric response of galvanometric negativity. 



Responses to uniform stimulus are sometimes of an 

 alternating character; this is exhibited by the mechanical 

 response of Mimosa and by the photosynthetic response of 

 Hydrilla. 



Light gives rise to dual effects, anabolic and catabolic, 

 the resulting effect being A— D. The A effect may become 

 masked by the D effect when the latter is relatively pre- 

 dominant. The A effect may, however, be unmasked by 

 the sudden stoppage of light, with resulting ' overshooting ' 

 of the response in the positive direction. 



Chemical agents cause characteristic reactions in the 

 plant. The effect of a minute dose of poison is often an 

 enhancement of physiological activity. 



Variation of the tonic condition affects all modes of 

 response alike, as shown in the depression of response by age 

 and by unfavourable conditions of the environment. In 

 specimens in a sub-tonic condition, stimulation enhances 

 the general physiological activity of the plant. 



