RELATION BETWEEN TEMPERATURE AND GROWTH 453 



condition of rest, but a dynamic condition of equilibrium, 

 and it will offer little effective resistance to excitatory con- 

 traction. We shall therefore expect that in growing organs 

 similar stimuli will induce responsive effects varying in pro- 

 portion to the changes of excitability in the tissue, under 

 different conditions. 



We saw, in the case of Crinum Lily, that the optimum 

 temperature was near 35 C, and that at this optimum the 

 rate of growth was something like one and a half to three 

 times as great as at 30 C. At 37 C. we saw, further, that 

 the rate of growth was again reduced, and had become equal 

 to, or lower than, that at 30 C. We might therefore expect 

 that, on recording the retardation of growth in response to 

 external stimulus at three definite temperatures, say 30 C, 

 35 C, and Z7° C., we should find it to be greatest at 35 C. 

 being in fact at that point about one and a half to three 

 times as great as at 30 C. The response at 37 C, on the 

 other hand, which is beyond the optimum, would be much 

 less than at 35 C, being equal to, or even less than, that at 

 30°C. 



Table showing Variation ok Excitatory Mechanical Response 

 at Different Temperatures 



I have made numerous experiments completely bearing 

 out these conclusions. The mode of experimental proce- 

 dure is as follows : a balanced record is taken at the given 

 temperature, and the growing organ is then subjected to a 

 definite intensity of stimulation, which may consist of tetanic 

 thermal or electrical shocks, lasting for twenty seconds. 

 Records are then made of the resulting contractile retarda- 



