;}. The assimilation under difTerent intensities of light. 



Tlie experimenls in Ihe inlluence of Iho lif^hl wilh normnl CO, 

 percentage (O.57 mg. per lilre of airj fully conlinn carlier obser- 

 vations. In tables I, IV, VIII, IX. X, and XII are incliulefl series 

 of experiments wilh Nastnrtiiiiu paliistrc, Ålriplex lalifoliiim, Slellnrin 

 nemorum, Oxalis Acetosclla, Melandrium riihnim, (Arcca ali)iiHi. I 

 found Ihat the sun-plants (Nasfurliiim and Ålriplex) followed a morc 

 uniformly bent curve than the shade-plants examinod. I'or Ihc 

 latter the curve showed a sharp bend at a cerlain ([iiile low inlensilv 

 of light, and then passed över into a line paralicl witli Ihc abscissa. 



Boysen-Jensen's curves (1918) for a numi)er of siiii- and slmde. 

 planls present a similar appearance lo mine. n()vsp;N-.Ii;Nsi:N bas 

 however coUected Ihe resulls from four shadc-i)lanls and shade- 

 forms respectively in a single skeleton curve (1918, p. .'U8), whicli 



Fig. 2. Diagram showing the influence of different intensities of light iipon the 

 ('0„ assimilation of certain shade-plants. The curve of Cirrra is almost identi<al 

 with that of Mclanäriimi and therefore was not drawii. 



can therefore have no pretensions to acciiracy. The vaUies which 

 he oblains for the Oxalis Acetosella also examined i)y me vary 

 extremely, and the horizontal part of the curve is considerably 

 lower than is indicaled by my values. While lk)Ysi;N-.Ii:Nsi:N 

 describes an optimal COg absorption"of only O... mg. per fiO cni.- 

 per hour, I have found under similar condilions a CO. absorplion 

 of 2.4 mg. Probably Boyskx-Jensens low values are in pari due 

 to bis not entirely satisfactory method of invesligalion. Il is of 

 course also possible that the somewhat dilVerent condilions in re- 

 gärd to transpiration and supply of CO. which Ihe experimenls 



