NO. 17 GROWTH OF ALGAE IN WAVE-LENGTH REGIONS MEIER 9 



The means for the three experiments were then determined. (See 

 table 3.) When the means of the nephelometric results are compared 

 with the means of the ratios of the cell counts, the same general result 

 is obtained. 



In figure i, a diagram is given of the cell multiplication for each 

 wave-length region superimposed on a diagram showing the relative 

 energy transmitted by each filter. The columns marked L and D indi- 

 cate results of daylight and darkness respectively. The blue region 

 produces the greatest amount of increase over the other regions, the 

 red and the yellow show considerable increase, the green gives a de- 

 crease, and the infrared shows no change. The daylight, the combina- 

 tion of all the regions of the spectrum, gives the largest increase of 

 all. Since, however, no measurement of the intensity of the radiation 

 stimulation was possible for daylight, the daylight results cannot be 

 considered exactly comparable to those of the filters where the radia- 

 tion stimuli are known to be equal. 



The nephelometric measurement, being a very indirect method of 

 measurement of cell multipHcation, since it is based on the turbidity 

 of the solution which doubtless undergoes a change during 2 weeks, 

 should not be regarded as anything more than a check on the results. 

 The cell counts give the definite result of the experiment. 



CELL LENGTH 



The lengths of 25 cells of each culture were measured and the 

 means were recorded in table 4. The accuracy of the width measure- 

 ments was not sufficient to show a possible increase of 20 percent. 

 Hence, assuming no increase in width or thickness, but increased 



Table 4. — Cell Length {mm) at Completion oj Experiments 



