NO. 21 CO2 ASSIMILATION AND WAVE LENGTH HOOVER Q 



In table 2, column i gives the wave lengths at the center of 

 the wave-length intervals, column 2 the fractional part of the total 

 energy transmitted by the filter in the various wave-length intervals, 

 column 3 the measured values of photosynthesis, and column 4 the 

 approximate amount of photosynthesis contributed by each wave- 

 length interval. The sum total of column 4 represents the amount 

 of photosynthesis originally measured as 257. 



A similar operation was performed for each 200 A wave-length 

 interval for the whole spectral region covered by the photosynthetic 

 measurements. These values represent the first corrected approxima- 

 tion to the photosynthesis and wave length curve. Subsequent cor- 

 rected approximations will be understood by what has been said in 

 the preceding paragraphs. 



In table 3, column A represents the measured values of photosyn- 

 thesis determined with the large Christiansen filters, and columns Aj, 

 A2, and A3 are the first, second, and third corrected approximations, 

 respectively. Column B represents the measured values of photo- 

 synthesis obtained with the small filters, and columns Bi, Bg, B3, 

 and B4 are the first, second, third, and fourth corrected approxima- 

 tions, respectively. Only small changes occur in the form of the 

 curves after the first corrected approximation in case of the large 

 filters, and after the second corrected approximation in case of the 

 small filters. 



FINAL RESULTS 



The final corrected results, in each case, have been plotted in 

 figure 4. Curve A3, the corrected form of the curve obtained with 

 the large Christiansen filters, is considered to be the curve nearest to 

 the true form of the photosynthesis-wave-length curve. 



The points on the original curve are based on the mean of five or 

 more determinations of the ratio between the photosynthesis pro- 

 duced at 5461 A and at the wave length at the given point. Individual 

 determinations did not vary on the average more than 4 percent 

 from the mean ratio. Thus we may assume that the original values 

 of the photosynthesis produced by the energy transmitted by the 



various filters are accurate to about -4^ percent or 2 percent. 



In correcting the original curve another source of error is possible. 

 The distribution of energy transmitted by the large Christiansen 

 filters was measured by a double monochromator on clear days, near 

 noon. Since the distribution of energy in sunlight varies with the 

 transparency of the air, it is not certain that the measured values 



