in Naaturlium paliislre, as has been said, at ahoiil ,.',, lij^ht. In Alri- 

 plex Ihe poinl of tMiuilihiium seenis lo be already reaolied al al)oul 

 ■^Q light (see lable XII). In llie suii|)lanl Siiutpis (ilhu, examined 

 by Boysen-Jenskn (1918), Ihe poinl of e(|uilibriuni seenis lo lie al 

 -^^- light, in the apple-leaves examined by Stai.iki.t 'H)20; al ^y 

 light. The sun-plants Iheiefore sceni quile geneially lo have Iheir 

 lighl-minimum 2 — 4 times higher Ihan the shade-planLs (cp. p. 76), 

 which parlly explains why Ihey cannot bear dceper shade. 



SUMMARY. 



The object in view has been to ascerlain the inlensily of assi- 

 milation in certain lypical forest-plants, viz. Oxalia Acetosella, Slel- 

 laria nemonim, Melandrium rubriim, and Circea alpina, under ddTe- 

 rent lights and supplies of CO2, and at the same lime to examine 

 Ihe conditions of lighl, the CO2 conce tration, and Ihe temperalure 

 of the habilats, in order to arrive at an idea of the produclion of 

 oiganic substance under the natural conditions. In addition lo the 

 forest-planls, a lypical shore-plant, Nasturtium paluslre,\\'as a\so more 

 closely examined. 



The eslimations of the assimilalion were carried out by means 

 of a new apparatus construcled for ecoiogical use. The principle 

 of this apparatus is Ihat the assimilation-chamber also conslitutes 

 an absorplion vessel for the carbon dioxide, which is estimaled över 

 a baryta solulion wilh a wide surface. The same apparalus was 

 used for the estimation of the respiration and of Ihe carl)on dioxide 

 of the air. For purposes of comparison Ihe usual melhod wilh an 

 air-current and absorplion in a PETTENKOFi:n lube was also employed. 

 — In the eslimations of the assimilation the follouing resulls were 

 obtained : — 



1. Wilh a variation of the lighl-inlensity and wilh normal (X),_, 

 percenlage in the air (O.57 mg. per lilre), curves of Ihe Hi.ackman 

 type were obtained for all the shade-planls. Wilh light up 10-5^0—5^0 

 the assimilation seems to be more or less proi)orlional lo the in- 

 tensity of light. Above j\^ light no furlher rise look place. 



For Nasturtium a curve of a more logarithmic patlern was ob- 

 tained. 



2. Wilh constant light the assimilalion rises wilh Ihe CO., supply 

 up to a certain height, which is delermined by Ihe light inlensily. 



