LONGITUDINAL RESPONSE OF RADIAL ORGANS 



75 



blades of the air-vane governor (fig. 36). The diagram 

 shows the mode of making successive closures of the electric 

 circuit for giving thermal shocks. And the same arrange- 

 ment serves to close the primary of the induction coil. 

 The duration of stimulus, depending upon that of the closure 

 of circuit, may be adjusted by varying the length of the 

 radial arm. The effective intensity of stimulation may be 

 increased by applying three or four shocks in rapid 



Fig. 36. Diagrammatic Representation of Apparatus for Periodic 

 Stimulation of Plant 



H, the wire cylinder made in hinged halves, periodically heated when 

 the electric circuit is closed by tilting over of balanced key, K, when 

 pressed by rod, R. v, air-vane of clock, by which period of rotation 

 is adjusted. 



succession, instead of one. For this purpose the radial arm 

 carries at its end a small plate, of which the margin is 

 divided into three or four teeth as the case may be. It is 

 thus possible to produce a stimulation which consists of the 

 requisite number of summated shocks. Or, instead of the 

 clock, we might, for the purpose of producing brief and 

 definite closures, have a metronome. But this is a less 

 perfect arrangement than that of the clock. 



