JOSEPH KRAPKA, JE. 429 



the Qt2-t, experimental values. For the 16-15° interval, Qio = 27.31; 

 for the 17.5-16° interval it is 3.28; there is a decrease in the value 

 from here as the temperature increases until at 33-31° the value is 

 0.89. 



I wish to point out here that above 29° the values of Qio really be- 

 come negative. 



Obviously Qio has no practical value for these reactions since its value 

 may lie anywhere between 27.31 and —2.41. A glance at Lehen- 

 bauer's data on the rate of growth of maize seedlings shows even a 

 greater departure from the theoretical 2-3 value of Qio. Here it 

 ranges from 32 at 15-13° to -428.2 at 42-45°C. Exceedingly high 

 temperature coefficients are suggestive of enzymatic reactions and 

 toxicity effects while the negative values suggest physical processes. 



Relation of the Temperature Effects on the Length of the Developmental 

 Periods to Those on Facet Number. 



We have seen that the facet curve can be superimposed on the theo- 

 retical Qio curve with a closeness that can hardly be attributed to 

 chance. The next obvious thing is to see how closely the facet and the 

 metamorphic curves agree. 



In Fig, 10, the facet curves for the Low Selected bar gtocks are su- 

 perimposed on the development curve. From 15-25° the two sets of 

 curves approximate each other very closely. Above 25°, the meta- 

 morphic curve decreases less rapidly, until above 29° it begins to 

 turn up again. The facet curves continue to decrease at their initial 

 rate. 



The reciprocal curves are of particular interest. That for the rate 

 of development gives approximately a straight line between 15 and 

 29°. It likewise shows an optimum at 29° with a subsequent decrease 

 in rate and further increase in temperature. The reciprocal of the 

 facet curve gives an exponential curve, without a decrease in rate at 

 the upper temperatures. The lower part of this curve approximates 

 the straight line features of the metamorphic curve. In other words. 



