40 



CHAP. IV. VARIATION OF TEMPERATURE 



5 mm. per minute. The recording lever inscribed successive 

 dots at intervals of a minute, during which the temperature 

 rose 1°. A Thermocrescent Curve was thus obtained, the 

 ordinate representing increment of growth, and the abscissa 

 the time as well as the rise of temperature. The curve 

 (fig. i6) shows growth at standstill at 22° C. The growth 

 was at first slowly increased with the rise of temperature, 

 and then more quickly. At 33° C. the rate of increase of 

 growth was very rapid, attaining its maximum at or about 

 34° C. At higher temperatures the rate underwent a rapid 

 decline, being reduced at 39° C. to about a fifth of the 



optimum rate. 



Determination of absolute rate of growth at different tem- 

 peratures. — The Thermocrescent Curve [see fig. 16) gives 

 sufficient data for the calculation of absolute rates of growth 

 at different temperatures. The vertical distance between 

 successive dots is the increment of growth in i minute for 

 a rise of 1° of temperature between T and T'. If / repre- 

 sents the magnified growth-elongation in millimetres for a 

 period of 60 seconds, and m the magnifying power of the 

 recorder, then the absolute rate of growth for the mean 



temperature 



is found from the formula 



Absolute rate of growth at 



T + T' / X io3 



[jL per second. 



2 ~ m X 60 

 The results thus calculated are given below in a tabulated 

 form. 



Table II. Rate of Growth for Different Temperatures (Kysoor). 



