_Temperature minimum: Experiment 59._--For the determination of the minimum, I took a specimen of _S. Kysoor_, and subjected it to a continuous lowering of temperature, by regular flow of ice-cold water in the outer vessel of the plant-chamber. Record was taken on a moving plate for every degree fall of temperature; growth was found to be continuously depressed, till an arrest of growth took place at 22°C. (Fig. 64). The arrested growth was feebly revived at 23°C., after which with further rise of temperature there was increased acceleration. The optimum point was reached at about 34°C. In some plants the optimum is reached at about 28°C., and the rate remains constant for the next 10 degrees or more. [Illustration: FIG. 64.--Record of effect of fall of temperature from 30°C. to arrest of growth at 22°C.] [Illustration: FIG. 65.--Effect of rise of temperature from 53°C. to 60°C. A sudden contraction, indicative of death-spasm, takes place at 60°C.] _Temperature maximum: Experiment 60._--For the determination of the maximum, the temperature was raised much higher. At 55°C. growth was found to be greatly retarded with practical arrest at 58°C. At 60°C. there occurred a sudden spasmodic contraction (Fig. 65), which I have shown elsewhere to be the spasm of death. This mechanical spasm at 60°C. is also strikingly shown by various pulvinated organs. An electric spasm of galvanometric negativity, and a sudden diminution of electrical resistance also take place at the critical temperature of 60°C.[U] [U] BOSE--“Plant Response,” p. 168; “Comparative Electro-Physiology,” p. 202, p. 546. I have described the immediate effect at the critical point. Long maintenance at a temperature few degrees below 60°C. will no doubt be attended with the death of the organ. Fatigue is also found to lower the death-point. THE THERMO-CRESCENT CURVE.