DAILY PERIODICITY OF GROWTH IN LENGTH. 



7A7 



I. The Thread-indicator is a simple contrivance in which the free end of the thread 

 which hangs down from the pulley and is kept tight by a weight of a few grammes, 

 carries a horizontal needle which moves freely over a graduated scale as the end of the 

 thread which is fixed to the plant rises with its growth. 



Fig. 451.— Autographic Auxanometer, fof recofding- the development during short periods of an internode of a growing 

 plant y,- ss' the lines scored by the index z on the blackened paper / fixed to the cylinder C which is made to rotate 

 eccentrically by means of the clock-work D. 



2. In the Arc-indicator the thread cf(¥\g. 450) fixed to the plant a is carried over 

 the pulley d and fixed to a pin which is attached to a second pulley g. An index z made 

 of a straight and firm straw is fastened to this second pulley in the radial direction, its 



