3i6 



PLANT RESPONSE 



drop of shellac varnish, the other end of the thread being tied 

 to the longer arm of the Optic Lever, which is 30 cm. long. 

 The distance of the recording drum from the mirror is also 

 30 cm. The length of the lever arm being thus equal to the 

 distance of the drum, and the extent of the angular move- 

 ment being by reflection doubled, it will be seen that the 

 movement is magnified twice. The thread is attached, 

 however, to the middle of the leaflet, and the record there- 



Eig. 125. 



Experimental Apparatus for Making Records of Pulsation 

 of Desmodium 



Leaflet, P, mounted in u-tube in plant chamber, and attached to long arm 

 of Optical Lever, L ; M, mirror attached to fulcrum-rod ; D, recording 

 drum ; 1, O, inlet and outlet pipes for gases and vapours introduced 

 into plant chamber ; c, electric heating coil. 



fore gives the movement of the tip unmagnified. The records 

 given in some of the figures are thus without magnification. 

 In others, again, the records are on a reduced scale. 



It will be understood here that the extent of movement 

 will vary with the length of the leaflet, some of these being 

 very small, and others relatively large. 



In the apparatus shown in fig. 125, the smaller chamber 

 contains the motile leaflets mounted in a tube filled with 

 water. By means of an inlet-pipe, different gases may be 



