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Researches on Growth and Movement in Plants by Means of the 



High Magnification Crescograph. 

 By Sir Jagadis Chundee Bose, assisted by Guruprasanna Das, L.M.S. 



(Communicated by Prof. S. H. Vines, F.E.S. Received October 19, 1917.) 



The auxanometers usually employed for recording longitudinal growth 

 allow a magnification of only 10 or 20 times. The growth of a plant is, 

 however, so slow that it requires several hours to detect the normal rate of 

 growth and its variation under any changed condition. It is, moreover, 

 impossible to maintain the external conditions absolutely constant throughout 

 the experiment ; even if this were possible, there would be some autonomous 

 variation of the rate of growth during such lengthy periods. Hence, there 

 must always be some uncertainty in the results obtained by a method which 

 requires long time for observation. The elements of uncertainty can only be 

 eliminated by reducing the period of the experiment to a few minutes, but 

 that would necessitate devising a method of very high magnification and 

 automatic record of the magnified rate of growth. 



I attempted to solve this problem by the employment of the optic lever, 

 where an axis carrying a mirror underwent rotation proportional to the 

 growth-elongation. The reflected spot of light magnified the movement of 

 growth from 1000 to 10,000 times. The vertical movement of the spot of 

 light was converted into a horizontal movement by means of a mirror 

 suitably inclined. The excursion of the spot of light was followed by means 

 of a pen on a drum revolving at a known rate ; or the record was obtained 

 automatically by photography. Hence a curve was obtained whose ordinate 

 gave growth-movement, and abcissa time.* 



Eecords thus obtained opened out a very extensive field of investigation on 

 growth and its variations under the manifold influences of environment. 

 The photographic method was automatic, but necessitated the discomfort and 

 inconvenience of a dark room ; the results, moreover, could not be followed 

 visually. The other method of obtaining the curve of growth by following 

 the excursion of the spot of light with a pen was far more convenient, but 

 the results in this case are likely to be affected by personal error. In order 

 to obviate all these difficulties I devised a direct method, in which the plant 

 by its own autographs exhibits the absolute rate of growth and the induced 

 variations in an extremely short period of time. I propose, in this paper, to 

 give an account of some of the researches which I have been carrying out 



* Bose, ' Plant Eesponse,' 1906, p. 421. 



