Researches on Growth and Movement in Plants. 



373 



I will now proceed to describe certain typical experiments which will 

 show : (1) the extreme sensibility of the crescograph ; (2) its wide applica- 

 bility to different investigations ; and (3) its capability of determining with 

 great precision the time-relations of responsive changes in the rate of growth. 

 In describing these typical cases, I give a detailed account of the experi- 

 mental methods employed, and thus avoid repetition in describing subse- 

 quent experiments. 



Expt. 1. Determination of the Absolute Rate of Groxoth. — I will describe 

 the results of a record on a stationary plate obtained with Kysoor. The 

 oscillation-frequency of the plate was once in a second, and the m,agnification 

 employed was 10,000 times. The magnified growth-movement was so rapid 

 that the record consists of a series of short dashes instead of dots (fig. 5, a). 



Fig. 5. — Crescographic records, a, successive records of growth at intervals of 1 second : 

 X 10,000, with a stationary plate. Effect of temperature : d, N, normal rate of 

 growth ; C, retarded rate under cold ; H, enhanced rate under warmth ; h, record on 

 moving plate, where diminished slope of curve denotes retarded rate under cold ; 

 c, horizontal record showing absence of growth in dead branch ; physical expansion on 

 application of warmth at arrow followed by horizontal record on attainment of steady 

 temperature, x 2000. 



For securing regularity in the rate of growth, it is advisable that the plant 

 should be kept in uniform darkness or in uniformly diffused light. So sensi- 

 tive is the method of record that it shows a change of growth-rate due to the 

 slight increase of illumination by the opening of an additional window. 

 One-sided light, moreover, gives rise to disturbing phototropic curvature. 

 With the precautions described, the growth-rate in vigorous specimens is 

 found to be very uniform. 



After the completion of the first vertical series, the recording plate was 

 moved 1 cm. to the left ; the tip of the recorder was brought once more to 

 the top by means of the fine screw adjustment S (fig. 3), and the record taken 

 once more after an interval of 15 minutes. The magnified record for 



