7.s 



EXPEEIMENT STATION. 



[Jan. 



fairly constant results are secured, according to our expecta- 

 tions. The records at the extreme ends of the scale, especially at 

 the upper cud, deviate considerably from the average, but this 

 was to have been expected, and for present purposes these rec- 

 ords may fairly be excluded. It seems proper further to throw 

 out three or four other records which on account of excessive 

 deviation are open to suspicion. With these apparently abnor- 

 mal records temporarily eliminated (they are to be studied 

 further in additional experiments), we secure results which 

 are rather remarkably uniform. Thus, the constant sum tem- 

 perature being computed to be 2,530 degree-hours, the extreme 

 deviation is less than 100, and the standard deviation is only 

 36.6°. The probable error is only 24. 7°. 1 



Thus, the temperature being known, and lying within reason- 

 able limits, the germination period of cress can be computed in 

 advance within a range of approximately two hours. 



The tabulated records used in these computations are ap- 

 pended to this report. 



A few abnormal records have been reserved for further study, 

 and there have arisen one or two intricate questions relating to 

 the whole theory of the physiological constant which must be 

 investigated further ; but as the figures stand they seem to 

 represent a considerable advance in this interesting field. 



Tabulation <>f Thermograph Records. 



i "Standard deviation" is the g etric mean of deviations. " Probable error" is de- 



flned ;is that departure from the mean, on either side, within which exactly one-half the 

 variates are found. 



