— 236 — 



a, that x percent of the diatoms divide every day and that none 

 of the diatoms are destroyed, the amount of diatoms after p days 



X 



will be m = a (1 + jqq) 3 * ; x is the percent production of matter 

 per day. In this equation m, a and p can be determined, hence x 

 can be calculated. For instance, when the amount of diatoms in 

 a certain volume of water at the beginning of the experiment is 100 

 and after 10 days 1000, the daily percent production can be cal- 



culated from the equation 100 (1 + jqq) 10 = 1000; x is found to 

 be 25.9. 25.9 % of the diatoms divide therefore every day. 



In a similar manner the percent production of matter can 

 also be found for higher plants, but only, when the whole or at any 

 rate a constant part of the new built organic matter is used to 

 form leaves. This condition is fulfilled in young seedlings, — for in- 

 stance in Sinapis alba. 



The determination of the percent production of matter by 

 Sinapis alba is carried out in the following way. 



The dry weight of 100 seeds of Sinapis is 0.5 g. 



2 Sinapis plants, who had grown from 5 — 27 Juni, 22 days, 

 (the time of germinating is not included) contained 0.442 g dry 

 matter, per 100 plants 22.1 g. 



The percent production of matter can then be calculated from 

 the equation 



0.5 (1+^ö) 22 = 22.1 

 x == 18.8 % 



3. Earlier experiments on the influence of light on C0 2 

 assimilation. 



Of investigations regarding the influence of light on G0 2 

 assimilation I shall mention only the most recent 1 ). 



Pantanelli (1903) dealt with the influence of light on the 

 bubbling rate in Elodea. The result of his experiments is recorded 

 in a curve (Pl. IV in his paper; cf. also Blackman and Smith 1911 

 pag. 408). He finds that the G0 2 assimilation is proportional to the 

 light intensity until about sunlight. At greater intensities of light 

 the C0 2 assimilation is diminished. The curve representing the 

 relation between intensity of light and G0 2 assimilation is therefore 



*) A detailed account on the influence of light on- plants may be found 

 in Combes (1910 p. 75). 



