47 



delermines Ihe inlensily of llie assimilalion. Aii inc-roaso in llir 

 assimilation can lluM-efore only lake i)lace i)y way of a raisinf; of 

 liie »limiting» or »conlrolling» niinimuni faclor. lloNVevcr, as will 

 be seen in Ihe foliowing accounl of my lescarclies, H[,a<:kman's 

 Iheory does not strictly a|)|)ly when liglil is llic niinimuni factor 

 opjjosed to the carbon dioxide. The sha|)e of cerlain assimilalion 

 curves also does not fully conforni to Iji.ack.mans idea (see also 

 O. Warburg 1919). 



My own researches are based on an ecological foundalion. I have 

 sel myself the task of examining the assimilation of various types 

 of phints under dilVerent external condilions realised in Nalure, wilh 

 a view to thus ascertaining how these jjlants are ada|)te(l to their 

 habilats. My material was a number of typical foresl-plants and 

 certain likewise typical shore-plants from Hallands Väderö, a small 

 island oIT the west coast of Sweden. The researches were carried 

 out at the Ecological Station on this island. 



Two or three slatemenls as to the influence of lighl on assimi- 

 lation in the case of sun-loving and shade-loving plants have already 

 appeared in the literature of the subject. Wi:is (19();}) determined 

 by means of the Bonnier-Mangin apparatus the intensily of assi- 

 milation in Oenothera and Polypodium. He found that in the sunlight 

 the assimilalion of carbon dioxide is from 2 to H times more po^verl'uI 

 in Oenothera. In -^q sunlight, on the other hand, Polypodium assimi- 

 lates more. Lubimenko's (1905, 1907) and Boysen-Jensen's researches 

 (1918) are more detailed. The latter determined the course of the 

 curves of light-assimilation in the sun-planls Sina])is alha, Senccio 

 sihyaticiis, Riimex Acetosella and Sambucus nigra, Ihe shade-plant Oxalis 

 Acetosella, and the shade-loving varieties of Senecio and Sambucus. 

 The result showed that the sun-plants in general have greater power 

 of utilising the intensive light than the shade-plants. My own re- 

 searches confirm this result. 



Information as to the influence of the carbon dioxide on Ihe 

 assimilation will also be found in the literature, and this will be 

 referred to below. But, on the other hand, no detailed examination 

 of the dependence of the plants upon the natural supply of carbon 

 dioxide or of the reciprocal inlluence of light and carbon dioxide 

 upon the form of the assimilation-curve has hitherto been altempted. 

 It is therefore upon these points that my own studies have been 

 directed. 



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