PLANT SCRIPTS 9 



varying effects of freshness and fatigue, of stimulating or 

 depressing drugs, of heat or cold, of the environment, are 

 in this way clearly revealed by the characteristic flexures 

 of the curve. Thus, by means of testing-blows, we are 

 able to make the plant itself describe those obscure 

 internal changes which would otherwise have entirely 

 escaped us. 



In fact, the phytographic records would, in the case 

 of plants, supply us with all the information that myo- 

 grams afford in the case of animal tissues. The experi- 

 mental difficulties which the plant offers are, however, 

 very great. In the case of muscle-contraction, the pull 

 exerted is considerable and the friction offered by the 

 recording-surface constitutes no essential difficulty, though 

 even here the time-relations of the curve are, I have reason 

 to think, rendered somewhat unreliable by this friction. 

 In the case of plants the contractile movement is relatively 

 feeble, and in the movement of the leaflet of Desmodium, for 

 instance, a weight so small as four-hundredths of a gram is 

 enough to arrest the pulsating leaflets. When employing 

 the very lightest lever, the extremely minute friction offered 

 by the smoked-glass surface of the recording-plate is sufficient 

 in this case to cause complete cessation of the record. 

 Even in the leaf of Mimosa, the friction offered is enough to 

 distort the curve to such a serious extent that errors are 

 introduced into the amplitude and time-relations amounting 

 to more than ^50 per cent. These difficulties have been 

 overcome by the successful devising of my Resonant 

 Recorder, an account of which will form the subject of the 

 next chapter. 



Summary 



Obscure modifications of internal condition of plant, 

 resulting from changing factors of environment, may be 

 revealed by records of plant's response to testing-blows. 



The relation between the impinging stimulus and the 



