W. J. V. OSTERHOUT AND A. R. C. HAAS 15 



stopped it would have produced enough of M so that (in spite of the 

 fact that M is constantly decomposing) the amount of M remaining 

 at the time, T, would be just enough to balance the loss, or 1 — e~^^ . 

 Hence if we start with nothing but 5 (the values of M and of P being 

 0) the amount of M present after the lapse of any given time T will 

 be 1 — e~^^ and the amount of P will be 



P = KT- (l-e-^^). 



This is the same as the equation 



P 1 1 „™ 



A K K 



when in the latter we put K = A 2iS was done in making the calcula- 

 tions given in Table I. Hence when we substitute the value K = 

 0.049 in the equation P = KT — {1 — e~ ), we obtain the values 

 already given in Table I. 



If the chlorophyll takes part in the reaction by decomposing or by 

 combining (as some recent evidence indicates), we might suppose 

 that S represents inactive chlorophyll, M active chlorophyll, and P 

 a derived substance which combines with CO2. At present it does not 

 seem profitable to attempt a more extended discussion of this question. 

 But it may be pointed out that (as one of us has recently emphasized)^^ 

 consecutive reactions of the type here discussed are to be looked upon 

 as the rule, rather than as the exception, in living matter. 



It is evident that either of the theories developed above gives a 

 quantitative explanation of the results. Both seem to be based on 

 reasonable assumptions. Future investigation must decide, which is 

 more useful. 



In any event, it is clear that much is to be learned concerning the 

 dynamics of photosynthesis, and it is hoped that the considerations 

 here set forth may be of value in this connection. 



SUMMARY. 



Minute amounts of photosynthesis in marine plants can be accu- 

 rately measured by adding a little phenolphthalein to the sea water, 



-^ Osterhout, /. Biol. Chem., 1917, xxxi, 585; xxxii, 23. 



