Researches on Growth and Movement in Plants. 375 



the rate of growth with rising temperature. In order to determine its 

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

 raising the temperature of the plant-chamher 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 by physical change abates in a 

 short time, whereas the change of rate of growth brought about by physio- 

 logical reaction is persistent. 



Having demonstrated the extreme sensitiveness and reliabihty of the 

 apparatus in quantitative determinations, I proceed to show its wide 

 applicability for various researches relating to the influence of external 

 agencies in modification of growth. For this two different methods are 

 employed. In the first, the records are taken on a stationary plate ; 

 the first in the series gives the normal rate ; the second is the record 

 taken under the given changed condition. The increase or diminution of 

 the space between successive dots in the two records at once demonstrates 

 the stimulating or depressing nature of the changed condition. In the 

 second method, the record is taken on a plate moving at a uniform rate 

 by clockwork. A curve is thus obtained, the ordinate representing 

 growth-elongation and the abscissa the time. The increment of length 

 divided by the increment of time gives the absolute value of growth at any 

 part of the curve. As long as growth is uniform, so long the slope of the 

 curve remains constant. If a stimulating agency enhances the rate of 

 growth, there is an immediate flexure in the curve. A depressing agent 

 lessens the slope of the curve. 



Expt. 3. — I will now give a few typical examples of the employment of the 

 crescograph for the investigation of growth ; the first example I shall take 

 is the demonstration of the influence of temperature. 



Stationary Method. — Fig. 5, d, gives records taken on a stationary plate. 

 The specimen used was Kysoor ; the crescograph magnification was 2000, 

 and the successive dots at intervals of 5 sees. The middle series, N, was at 

 the temperature of the room. The next, C, was obtained with the tempera- 

 ture lowered by a few degi'ees. Finally, H was taken when the plant- 

 chamber was warmed. It will be seen how under cooling the spaces between 

 successive dots have become shortened, showing the diminished rate of 

 growth. Warming, on the other hand, caused a lengthening of the spaces 

 between successive dots, thus demonstrating an enhancement of the rate of 

 growth. 



