{VA 



aboul Ivvice Ihe normal, in Oxalis Ihe maximilin increase was :i.^ 

 limes Ihe normal. 



It might possibly be snspecled Ihal llic increascd consumplion ol 

 CO.3 wilh ^\, light was only due lo absorplion. and Ihal llicrcroic 

 the figures oblained do not denolc increase in assimilalion. To lliis. 

 however, it may be objecled Ihal Ihe CO,, aljsorplion demonslialed 

 even in darkness l)y Willstättkk and Sroi.i. P.llM onlv amounls 

 to inlinilesimal values at the low partial |)ressurt' nsed in my ex- 

 periments. From Willstätti:r's experiments (It)l(S, p. 218) il appears 

 that e. g. 20 g. of Helianlluis-leaj^ at a CO2 concenlralion of 1 vo- 

 lume i)er cent absorb 3.2 mg. of CO.^, which corresponds lo aboul 

 0.25 mg. per 50 cm. 2 of leaf-surface. The COo concenlralion in my 

 experiments never reached more than 0.^5 volumes per cenl. This 

 low concenlralion, on exlrapolarising according lo Wii.i.stättkhs 

 curve (1918, p, 179, fig. 11), wonld produce an absorplion of less 

 than 0.09 mg. per 50 cm.-, and Iherefore a (piile inlinilesimal (|uanlily. 

 WiLLSTÄTTER obtained similar values wilh various olher leaves. 



Experiments wilh prolonged time of assimilation also show Ihal 

 the consumption of CO .3 j)roceeds conlinuously wilh a cerlain ve 

 locity, and Iherefore cannot be dependenl upon a primary absori)lioii. 

 which would of course proceed wilh diminishing velocily. Two 

 experiments were carried oul wilh SteUaria ncmonini at ^\, lighl and 

 with about 40 % longer assimilalion-lime (Table III, nos. 6 and 7). 

 No weakening of the CO.^ consumption can be observed, and Ihe 

 values fit in well, along wilh the olhers, lo the curve given in lig. Ii. 



The same is the case wilh the Oxalis leaves. In table VII, ex- 

 periment no. 1 was carried out wilh 50 ?», experiment 5 wilh 150*^ 

 longer assimilation-time than the other experiments. Here loo Ihe 

 values adapt themselves very well to Ihose obtained wilh Ihe nor- 

 mal time of expetiment (1 hour). 



Still more convincing are experiments 3 and 5 in lable VI, which 

 were performed with twice as long time as Ihe olhers. In Ihese 

 cases also the consumption of CO.^ is Iherefore independenl of Ihe 

 lime. — 



The experiments performed with electric light' show Ihat even al 

 about T^Q lighl, just as at '^\, the CO., supply increases Ihe assimi- 

 tion in a direct proporlion (see the table and ligs. 5 and 6\ Al 



' I used in the experiments a 500-watt Azo lamp, the Imlb of which was at a 

 (listance of about 30 cm. from the object. A 2 cm. layer of riinning water Howed 

 över the glass tover (cp. p. 49\ 



