AUTONOMOUS ACTIVITY OF GROWTH 42 1 



variation in the course of less than a minute, during which 

 time other conditions can be maintained absolutely constant. 

 The record shows that growth is a pulsatory phenomenon 

 (p. 18). The Magnetic Crescograph gives an amplification 

 of more than ten million times, thus making possible the 

 measurement of the smallest movement of growth and its 

 slightest variation. The sensitiveness of the method of 

 record has further been increased by the use of the Method 

 of Balance, in which the movement of growth is exactly 

 compensated by an equal movement of the plant down- 

 wards, the upsetting of the balance upwards or downwards 

 being due to induced acceleration or retardation of growth. 

 The Method of Balance offers a unique opportunity for 

 determination of the influence of the Time-Factor — that 

 is to say, of the effect on the reaction of the duration of 

 the action of an external agent. 



Autonomous Activity of Growth 



All autonomous movements are dependent on the 

 following conditions : 



1. Sufficiency of internal hydrostatic pressure in the 



active cells; 



2. Supply of energy for the maintenance of the normal 



tonic condition of the active cells ; and 



3. An adequate temperature. 



Ejfed of variation in the rate of ascent of sap. — It has been 

 observed in both motile and growing organs that increase 

 or positive variation of turgor, due to enhanced rate of ascent 

 of sap, induces an erection or positive response of a motile 

 organ, and a positive variation or enhancement of the rate 

 of growth. A diminution or negative variation of turgor, 

 due to withdrawal of water, induces a negative response of 

 a motile leaf, and a negative variation or retardation of the 

 rate of growth (p. 55). 



Effect of suhtonic condition. — When the energy stored 

 for the maintenance of the autonomous activity becomes 



