July 15, 1920] 



NATURE 



615 



Researches on Growth of Plants. 



By Sir Jagadis Chunder Bose, F.R.S 



I. — The High Magnification Crescograph. 

 NVESTIGATION on growth is a matter 



of 

 much practical importance, since the world's 

 food supply is intimately dependent upon vegeta- 

 tive growth. The movements of stems, leaves, and 



time. If a stimulating agent enhances the rate 

 of growth, this fact is exhibited by a flexure in 

 the curve upwards ; a depressing agent, on the 

 other hand, lessens the slope of the curve 

 (Fig. 2b). 



Precautions against Physical Disturbance. — The 



roots under the action of various forces, such as j effect of vibration may be neutralised by placing 



light, warmth, and gravity, are often due to 

 minute variations in the rate of growth. The 

 discovery of laws relating to the movement of 

 growing organs thus depends on the accurate 

 measurement of normal growth and its changes. 

 The great difficulty of the investigation arises 

 from the extraordinary slowness of growth, the 

 average value of which per second may be taken 

 as T^j^njjjj in., or half the wave-length of sodium 

 light. The " auxanometers " usually employed 

 produce a magnification of about twenty times. 

 Even here several hours must elapse before 

 growth becomes perceptible, but during this long 

 period the external conditions such as warmth 

 and light would necessarily change, thus vitiating 

 the results ; moreover, autonomous variation of 

 growth appears during lengthy periods. The 

 elements of uncertainty can be removed only by 

 reducing the period of experiment to a few 

 minutes ; but that would necessitate devising a 

 method of very high magnification and the auto- 

 matic record of the magnified rate of growth. I 

 have been successful in this by my device of the 

 High Magnification Crescograph, consisting of a 

 system of two levers ; the first magnifies a 

 hundred times, and the second enlarges the first 

 a hundredfold, the total magnification being 

 10,000 times. The various difficulties connected 

 with the weight and friction at the bearing have 

 been fully overcome.^ The further difficulty in 

 obtaining an accurate record of growth movement 

 arising from friction of continuous contact of the 

 writing point was removed by an oscillating 

 device by which the smoked glass plate moves to 

 and fro at regular intervals of time, say one 

 second (Fig. i). The record consists of a series 

 of dots, the distance between successive dots 

 representing magnified growth during a second 

 (Fig. 2a). 



The records may be taken on a stationary plate, 

 first under normal, and then under changed, ex- 

 ternal conditions. The increase or diminution of 

 space between successive dots in the two series 

 demonstrates the stimulating or depressing nature 

 of the changed condition (Fig. 2d) ; or the record 

 may be taken on a plate moving at a uniform 

 rate. In the curve thus obtained the ordinate 

 represents growth-elongation, the abscissa the 



1 For a fuller account see the author's " Researches on Growth and Move- 

 ment in Plants by means of the Hi^h Magnification Crescograph," Proc. 

 Roy. Soc., B, vol. ex., iQig. (The diagrams are reproduced with the kind 

 permission of the Royal Society.) .Mso the following works published by 

 Messrs. Longmans, Gre-n, and Co.: — "Response in the Living and 

 Non-living" (1902); "Plant Response" (iqo6); "Comparative Electro- 



'Irritability of Plants^' (1913); " Life-n 



india-rubber sponges under the legs of a heavy 

 table supporting the apparatus. It is preferable 

 to screw the supporting bracket on a wall. I 

 have, indeed, been able to secure a magnification 

 of ten million times with my Magnetic Cresco- 

 graph in public demonstrations in busy London,. 



tiysiology" (1907); " 

 'lants," vols. i. and ii. (1918-19). 



-movements in 



NO. 2646, VOL. 105] 



Fig. 1. — I'he High Magnification Crescograph. P, plant ; S, S', 

 micrometer screw for raising or lowering ihe plant ; C, clock- 

 work for periodic oscillation of plate ; K, crank ; \V, rotating 

 whetl. 



the indication of the instrument being quite un- 

 affected by the street traffic. In Fig. 2c is given 

 the record on a moving plate taken with the High 

 Magnification Crescograph. A dead twig had been 

 substituted for the growing plant, and a per- 

 fectly horizontal record demonstrated the absence 

 not only of growth, but also of all disturbance. 

 There is an element of physical change in experi- 

 ments on variation of the rate of growth under 

 artificially raised temperature. In order to deter- 

 mine its character and extent, a record was taken 

 with the dead twig of the effect of raising the 

 temperature of the plant-chamber through io° C. 

 The record shows that there was an expansion 

 during rise of temperature, which, however, 



