NO. 21 CO2 ASSIMILATION AND WAVE LENGTH HOOVER 7 



CORRECTION OF CURVES FOR STRAY LIGHT 



These curves of photosynthesis and wave length may be regarded 

 as approximately correct, but need improvement because the Christian- 

 sen filters, besides the predominant wave lengths, transmitted others in 

 lesser degrees. 



Consider, for example, any wave length, as at the blue maximum 

 of curve A in figure 3, connecting photosynthesis and wave length. 

 For brevity call such a wave length Wo. On either side of this spectral 

 point consider equal wave-length intervals of width a to be set off. 

 Thus we reach wave lengths [Wo — ^iial, [Wq — (in—i)a], .... 

 [Wo-a], [Wo] [Wo + a], , [Wo+(n-i)a], [Wo + na]. Con- 

 sider this succession of equally spaced wave-length places to extend 

 from the wave length [Wo — ma], where the Christiansen filter ceases 

 to transmit shorter waves appreciably, or else where photosynthesis 

 sensibly ceases, to the wave length [JVo + na] where it ceases to trans- 

 mit longer waves appreciably, or else where photosynthesis sensibly 

 ceases. 



We have now to deal with two curves : i, the approximately deter- 

 mined curve of photosynthesis and wave length; 2, the curve of 

 energy transmission and wave length for that Christiansen fiher which 

 transmits predominantly the wave length Wo- 



Let [^0], [e-m] .... [^-1], [^+1] .... [^+"1 represent the ordi- 

 nates of curve no. i at the wave length region Wo and at wave lengths 

 situated at equal intervals of width a on either side, thus covering 

 the whole range of spectrum from the place [Wo — nia] to [Wo + na]. 

 Let [Co], [C_„,] .... [C_x], [Gx .... [C,^] be the areas in- 

 cluded under the curve no. 2 above described, within intervals of 

 wave length a from the wave length [Wo — ma] to the wave length 

 [Wo + na]. These areas will be proportional respectively to the energy 

 transmitted by the Christiansen filter which transmits predominantly 

 the wave length Wo, but whose transmission extends in sensible degree 

 all the way between wave length [Wo — ma] and [Wo + na]. The sum 

 total of these areas we may call q, proportional to the total amount 

 of energy of radiation transmitted by the filter. If we divide the 

 measured areas [^_,„] .... [<?+»] by the sum total of these areas, 

 the new values of [e^,n] .... [e^n] will represent the fractional 

 part of the total energy q in each wave length interval a from the wave 



length [Wo- ma] to [IVo + na], and 2(^-m e^„) = i. 



Inasmuch as the curve no. i described above represents approxi- 

 mately the dependence of ])hotQsynthesis on wave length, therefore 

 the products [e.,nC.,n] . ■ ■ ■ [coCo] • • • • [c.nC.n] will each repre- 



