PHYSICAL DISTURBANXE I7 



rising temperature. In order to determine its character and 

 extent, a record was taken, with a dead twig, of the effect 

 of raising the temperature of the plant-chamber through 10°. 

 The record, with a magnification of 2000, shows that there was 

 an expansion during the rise of the temperature, after which 

 there was a cessation of physical movement, the record 

 becoming once more horizontal. The obvious precaution to 

 be taken in such a case is to wait for several minutes for the 

 attainment of steady temperature. The movement caused 



Fig. 6. Effect of variation of temperature on a dead branch, 



taken on moving plate. 



Horizontal record shows absence of growth and freedom from 

 physical disturbance. Physical expansion on application of 

 heat at arrow is followed by horizontal record on attainment 

 of a steady temperature. (^Magnification 2000 times.) 



by physical change abates in a short time, whereas the 

 change in the rate of grow^th brought about by physiologi- 

 cal reaction is persistent. 



Having demonstrated the extreme sensitiveness and 

 reliability of the apparatus for quantitative determination, 

 I now demonstrate its wide applicability for various 

 researches relating to the influence of external agencies in 

 modification of growth. 



Experiment 4. Effect of variation of temperature on 

 growth. — The record was taken on a stationary plate with 

 a different specimen of Kysoor. The magnification was 

 reduced to 2000 ; but the interval between successive dots 



