()1 



furlher rise in the CO2 concentralion Ihe inlensily of assimilation 

 remains constant. 



It is however my opinion that tiie limit often depends iipon llie 

 closure of the stomata. In Oxalis, for examplo, one series of ex- 

 periments shows a limit at 4 mg. C()2 assimilation. In anolher 

 series the limit was not reached even at a rale of assimilation of 

 aboul 7 mg. (see Table V and fig. 5). 



z 



4 



14 



I 



Fig. 5. Diagram sbowing the influence of CO., snpply 011 the C0.> assimil.ition 

 of Oxalis Acetosclla at different intensities of light. 



Illustrations of the statements mentioned will be seen in Ihe 

 curves for Nasturtiiim pahistre and Viola al ,'^ light, for Oxalis at 

 ca. J light, and for Oxalis, Slellaria nemorum and Melandriiim rnbnim 

 at Jö 1'gl^t- These curves show a very good agreement with the 

 curves found for Elodea and Fontinalis by Blackman and Smiih 



(1911, p. 392, fig. I). 



Whelher the rising arm of the curvé should be considered mathe- 

 malically as a straight line or as part of a curve very ilat in the 

 initial portion, cannot with certainty be decided eilher in regard 

 to Blackman and Smith's experiments or to mine. To decide Ihis, 

 very numerous experiments with particularly pure material wonld 

 be re(iuired. It may very well be that the statement made about 



