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68
and a falling atmospheric pressure also have a favourable effect
upon the CO, production of the ground, since the ground-air is
then sucked up from the pores of the earth.
So as to obtain an idea of the quantities of CO, which the plants
examined by me have at their disposal in their habitats, I under-
took during the end of August and beginning of September, 1920,
a few estimations of the quantities of CO, 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 placed on a wire stand, and was filled
with 25 ccm. of 2, baryta solution. Then there was placed over the
whole a glass bell, the edges of which were pressed down into the
soil to prevent diffusion. 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 CO, was given off by a patch of ground of given size during
the given time. The results are shown in the following table:
Production of CO, from the soil
Date Place [ | Meteorological CO, produced from
| | t conditions |. .90 em.? soil
| |
25. VIII | The shore. Zone of Sunshine. 18° in 0.58 mg.
2X sand-algas. the shade. 0.57 »
Mn » »
| VILL Alder-swamp. Slightly gloomy Oise me
9.30 a. m. Circea-association. weather. 15°. x:
"ptr PNE
12. VIII Alder-swamp. Gloomy weather. 1.02 mg.
21 VII | Dry spot. Oxalis- | 16? 116 »
aan | association. | 15° 1.25 »
| Alder swamp.
| 21. VIII Naked soil. 16° lan rt
| 12 noon Carex vesicaria, | E,
| Peucedanum palustre. |
[315 VIII Beech forest. | - 1.35 mg.
[C p. m. EO vegetation. 157.5 | 1.88 »
| 31. VIII m | | | ;
| Bio LD et irs on Sunshine. 15° ae mg
| —8 p. m. 1e shore. 2.64 >
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