CHARACTERISTIC DIFFERENCES IN RESPONSE 



173 



Determination by the Method of Bubbling. — The action of 

 the same red and blue lights was compared by the Method of 

 Bubbling. The sequence of experiment was : (a) Determina- 

 tion under direct sunlight ; (b) under red light ; (c) under 

 blue light ; (d) once more under sunlight. The following 

 are the results : 



(a) Activity under sunlight 



(b) „ „ red light 



(c) „ „ blue light 



(d) „ „ sunlight 



B : R : S : : n-6 : 24 : 95 : 



95 

 24 



n-6 



94 



2:8-2 



(4) 



Thus with different specimens and by the employment 

 of two different methods we obtain the following ratios : 



The relative values of photosynthesis under the different 

 lights are thus seen to be practically the same in all the 

 experiments. 



Having determined the effects of the red and blue, I next 

 attempted to find those of other lights ; but the yellow, 

 orange and green glasses did not give pure monochromatic 

 light. It is possible to cut off the impure constituents in 

 the light by the use of multiple screens, but the intensity 

 of radiation then undergoes so great a diminution that 

 the photosynthetic activity becomes diminished or even 

 abolished. We have to remember that the colour or wave- 

 length of light is but one of the two factors in its photo- 

 synthetic action, the other being its energy of radiation. 

 This will be understood from the following experiment. 

 The light transmitted through a single sheet of red glass 

 was, as we have seen, more effective than that transmitted 

 through a single piece of blue glass. If instead of a single 



