The level of significance for both regression 

 lines according to the F test is >99.5 percent 

 for both sets of data. Dashed lines on the 

 figures indicate 95 percent confidence bands. 



The variability of these data prompted us 

 to determine the heat content of the ex- 

 tracted fuel to see if a seasonal trend was pres- 

 ent. These data are also presented in table 3. 

 The extracted leaves gained approximately 

 171 B.t.u./lb. from spring to fall. The stems 

 gained 148 B.t.u./lb. 



Assuming that the difference between the 

 heat content of the total fuel and the heat 

 content of the extracted fuel, AH, is due sole- 

 ly to extractives, we plotted AH against ex- 

 tractive content (figs. 8 and 9). The coeffi- 

 cient of determination, r^ , is 0.60 for leaves 

 and 0.44 for stems. The data were determined 

 to fit a linear line and the equations are 



Leaves: Y = 156 + 82.2X 

 Stems: Y - 120 + 78. OX. 



The level of significance of the regression line 

 is >99.0 percent according to the F test. 



This relationship is complicated by the 

 likelihood of seasonal variation in the heat 

 content of the extractives themselves. There- 

 fore it was necessary to determine this for the 

 samples. The heat content of the ether extrac- 



tives was calculated by the following relation- 

 ship: 



(1 — fraction ext.) • (Hex) + fraction ext. • 



(Hext) = Htot 

 where 



fraction ext. - extractive content 



(fraction dry weight) 

 Hex ^ heat content of the 



extracted fuel (B.t.u./lb.) 

 Hext ^ heat content of the 



extractives (B.t.u./lb.) 

 Htot ~ heat content of the 



total fuel (B.t.u./lb.). 



Heat content of the extractives calculated 

 from 14 samples was 

 Leaves: X = 15,564 



Range = 3,933 (13,445 - 17,378) 

 Stems: X - 19,012 



Range = 7,321 (17,212 - 24,533). 



The average heat content of leaf extractives 

 from three of the 1963 plants was found to 

 be 15,679 B.t.u./lb. by actual measurement. 



There is a direct relationship for leaves be- 

 tween extractive content and heat content of 

 the total fuel (Htot)- This implies a seasonal 

 trend in Hext ^or leaves. For stems, the trend 

 does not appear to be the same, since the 

 values remain fairly constant during summer 

 and fall. 



800 



360 



8.00 8.50 9.00 9.50 10.00 10.50 11.00 



ETHER EXTRACTIVES(Percent dry weight) 



Figure 8. — The relationship between AH and the ex- 

 tractive content of the leaves. 



550 



<1 450 - 



250 



2.00 ?.00 4.00 5.00 6.00 7.00 8.00 



ETHER EXTRACTIVES (Percent dry weight) 



Figure 9. — The relationship between AH and the ex- 

 tractive content of the stems. 



8 



