486 PLANT RESPONSE 



of Crinum Lily, which had been taken from the same flower- 

 head, and in which different constitutions were artificially 

 induced by carrying out the experiments at 30 C, 34 C, 

 37° C, and 44 C. The records were taken under balanced 

 conditions. 



On making an application of a solution so strong as 10 

 per cent, to a specimen at the normal temperature of 30 C, 

 the result was always a depression which set in immediately ; 

 but when the tonic condition of the plant was exalted, by 

 raising the temperature to a point near the optimum — that is 

 to say, to 34 C. — the same reagent was found to induce an 

 excitatory effect, its depressing action being postponed for 

 a considerable length of time. The effect obtained at the 

 temperature of 37 C. was very instructive. Responsive 

 excitability at this temperature has been shown to be almost 

 the same, if not indeed slightly lower, than that at 30 C. 

 But we should remember that in these two cases we have very 

 different histories ; for if in the former — that is, at 30 C. — 

 we have a normal amount of latent energy, then it is clear 

 that in the latter — that is to say, at 37 C. — there must be an 

 excess of latent energy. And as the result of this we see 

 that, while at 30 C. the growth-response showed immediate 

 depression, at 37 C. it offered a considerable resistance, as 

 seen in the temporary exaltation of response. Still more 

 interesting, however, was the effect at 44 C. At this tem- 

 perature it will be remembered that there was an apparent 

 arrest of growth, often supposed to be due to the setting-in 

 of heat-rigor. I have shown, however, that, so far from this 

 being the case, there is still at 44 C. a good deal of rhythmic 

 activity, the cessation of growth being due to the fact that in 

 the multiple response of growth each constituent response and 

 recovery had become equal. The presence of this activity at 

 44 C. becomes quite clear, when we find that the application of 

 salt at this temperature has the effect of renewing for a time 

 the resultant growth which had been in abeyance (fig. 199). 



Effect of poisonous solution of copper sulphate. — The 

 influence of constitution in determining resistance to adverse 



