68 



and a falling atmospheric pressure also have a favourable effecl 

 upon Ihe CO.^ production of the ground, since llie ground-air is 

 then sucked up from Ihe pores of Ihe earlh. 



So as lo oblain an idea of llie (juantities of CO2 which Ihe plants 

 examined by me have at Iheir disposal in Iheir habitats, I under- 

 took during the end of August and beginning of September, 1920, 

 a few estimations of the quantities of CO2 given off by the ground 

 to the air. The method used was very simple: A glass dish 10 cm. 

 wide, with a low edge, was phiced on a wire stånd, and was lilled 

 with 25 ccm. of "^^ baryta solution. Then there was placed över the 

 whole a glass bell, the edges of which were pressed down mto the 

 soil to prevent dilTusion. After a certain time the baryta was ti- 

 trated, and then, after subtracting the carbon dioxide present in the 

 air of the bell from the beginning, it was possible to calculate how 

 much CO2 w^as given ofl' by a patcli of ground of given size during 

 the given time. The results are siiown in the foUowing table: 



Production of C0„ from the soil 



