^9° GROWTH 



Care must be taken to have the instrument on a solid stand or 

 support, and while a proper supply of water must be given the 

 plant, yet no disturbance of the organs attached to the instru- 

 ment must be made. Careless handling of the lever may exert 

 intense stretching pulls upon the plant which may vitiate the re- 

 sults for several hours, by calling out the reactions to such stimuli. 



The data obtained by the auxanometric measurements should 

 be expressed in graphic form by means of a curved line. Take 

 the smoked paper from the cylinder, cutting it by a single verti- 

 cal slit. Lay in a shallow dish of sufficient size and flood with a 

 solution of shellac in alcohol. Hang up and allow it to dry. 

 Secure some double ruled paper with squares of a millimeter arid 

 centimeter. Begin at the lower left hand corner of the paper 

 and pass along the lower line of the ruled portion to the first 

 centimeter interval. Disregard the amount of elongation shown 

 during the first hour after the instrument was adjusted. Meas- 

 ure the length of the vertical line representing the second hour's 

 growth, and measure five times its length on the vertical line at 

 the first centimeter interval on the paper placing a dot to mark 

 the point. Transfer the measurement of the second hour, to the 

 next line "on a centimeter interval on the paper, and so on until all 

 of the records have been placed on the ruled paper. Now con- 

 nect all of the dots by a line and the resultant curve will show 

 the relative amounts of growth at different parts of the day, and 

 if the record is continued will embrace the grand period of growth 

 of the organ. Transfer the record of the thermograph to the 

 same paper and the influence of temperature upon growth may 

 be seen directly. Care must be taken that the records of the 

 auxanometer and thermograph for the same hour are placed one 

 directly above the other. 



370. A Precision Auxanometer and its Use. Difficulty may be 

 encountered in securing plants that grow with sufficient rapidity 

 to be capable of measurement by the simple lever auxanometer, 

 in which instance the form shown in Fig. 139 will be found more 

 useful. This type of instrument is sufficiently delicate in its ac- 



