Harry F. Clements 461 



In order to develop this equation for sugar cane, I have taken the 

 factors of maximum and minimum temperatures, radiant energy, and 

 the two dominant physiological factors, tissue moisture and age, and 

 have calculated the partial regressions for growth units. Vigor of plants 

 is not directly used here, although it will be remembered that among 

 other factors, moisture and age were dominant influences on factors 

 of plant vigor. The results of this analysis are shown in Table VII. The 

 five factors show a well-balanced assumption of influence on growth 

 units. 



TABLE VII 



Partial Regressions of Certain Factors on Growth Units 



(» = r 373) 



Factor 



Beta 



"/" Value 



Light 



Sheath moisture 



Age 



Maximum temperature (°F.) 



Min mum temperature (°F.) 



R= .8617 



From these data, the following equation evaluating the weight of each 

 factor on growth units was obtained : 



E = 0.0820XJ -\- 9.3206X0 — 0.0979X3 -f- 2.8025X4 +3.2272X5 — 1 130.9004 



where X r is the average daily radiant energy expressed as gram calories 

 per square centimeter per day; X 2 is the sheath moisture expressed as 

 percentage of green weight; X 3 is the age expressed in days; X 4 is the 

 maximum daily temperature as degrees Fahrenheit; and X 5 is the mini- 

 mum temperature expressed in degrees Fahrenheit. E is the estimated 

 average number of growth units produced per day. 



When this equation is applied to the pertinent data collected in this 

 study and the average daily growth units are multiplied by the actual 

 age of the crop in months, the results are as shown in Table VIII. 



The fact that the averages of the two columns are so very close is 



