86 



In Nasturtium and Viola tricolor at ^ light and in Oxalis and Me- 

 landrium at -^^^ lighl an ap[)r()ximate direct proporlionalilj' was ob- 

 lained beUveen Ihe CO2 concentralion and Ihe intensily of assi- 

 milation. In olher cases tbe assimilation rose more slowly than the 

 CO 2 concenlration. 



.'{. An increase of the CO2 absorption wilh abnormally high CO2 

 concentration in the air was observed even with small quanlilies 

 of light (^'(j). From this fact it may be concluded that the light 

 and the carbon dioxide mutually affect each other's influence as a 

 controlling factor, — 



The examination of the natural conditions gave the following 

 results: — 



4. The CO2 production of the ground during the period of ve- 

 getation atlains considerable values. It is least for sandy soil, great- 

 est in Ihe mould of beech-woods. Very abundant COg production 

 goes on in rotting beds of seaweed. 



ö. In Ihe forest, on account of the COg production of the ground, 

 the air is rich in carbon dioxide, especially nearest the ground, 

 ^vhere herbaceous plants live. The CO2 percentage may here rise 

 to more th;in twice the normal. This increased supply of CO2 is 

 an important condilion for the exislence of the shade-flora. 



6. The supply of light in the forest varies extremely, owing to 

 the passage of the sunlight through the tree-tops. Patches of direct 

 sunlight fall from time to time upon the ground, and this fact is 

 of importance for the assimilation of the foresl-plants. 



7. The conditions of temperature prevailing in the forest, as 

 \vell as the moisture and the proteclion from wind. are favourable 

 to an anatomical léaf-structure such as allows of the ulilisation of 

 the li^ht to the fullest possible extent. 



8. The iiitensity of respir ition is lower in the shade-plantsthan 

 in Naturtium and olher sun-plants. An equilibrium between re- 

 spiralion and assimilation is re'ached in the case of the shade-plants 

 at ,^p — ]^y light, wilh normal air. In order that Ihe daily assi- 

 milation may compensale the respiration of the nighl-time there is 

 required al 18" an average illumination of ^'tj light. In order that 

 the grovvth of the vegetation may be mainlained there is further 

 re(}uiied, in Ihe case of Oxalis, a minimum daily illumination of for 

 example I liglit for somewhat more than 1 hour. 



9. Among the shade-plants Oxalis has the greatest maximuni 



