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SMITHSONIAN MISCELLANEOUS COLLECTIONS 



VOL. 87 



percentage the results should be multiplied by .000041, the calibration 

 constant of the instrument. To express the assimilation rate in cubic 

 centimeters of carbon dioxide per minute the results should be multi- 

 plied by 0.025, i. c, 0.000041 x6oo. 



Two experiments were performed. In the preliminary one certain 

 difficulties were encountered which suggested the procedure followed 

 in the second experiment. A number of points of interest, however, 



Fig. 3. — Light-assimilation curves from lirst experiment uncorrected for growth. 



Ordinates, carbon dioxide assimilated. Multiply by 0.025 to obtain cubic 



centimeters per minute. 

 Abscissas, light intensity. Multiply by 3.56 X 10'* to obtain watts/cm". 



Multiply by 4.Q6 to obtain foot-candles. 

 Parameters, carbon dioxide concentrations. Multiply by 0.000041 to 



obtain volume per cent. 



brought out in the first experiment make it worth while to present 

 both experiments. 



PRELIMINARY EXPERIMENT 



On a given day the plants were supplied with air containing a 

 given concentration of carbon dioxide and the rate of photosynthesis 

 determined for six light intensities. This procedure was repeated 

 on other days for different concentrations of carbon dioxide. The 

 results of this series of experiments for several concentrations are 

 given numerically in Table i and graphically in Figure 3. 



