()9 



The results show a varying CO.^ produclion in (liffcrcnl soils. 

 That cleaii sandy soil should show Ihe wcakesl CO,, produclion 

 causes no surprise. No appreciahle deconiposilion hikcs |)l;icc licie, 

 bul on Ihe olher hand Ihere are found e. g. iron l)aclena. Tlie COg 

 produclion from an open damp surface of sandy soil hy the soa- 

 coast is only half as great as in Iht- förest. In beech-wood mould 

 covered wilh fallen leaves Ihe C()2 produclion was strikingly high. 

 The mould is loose and aeraled, and is distinguished hy hvely hac- 

 terial aclivity. The CO.^ produclion here is more Ihan '.] limes as 

 great as on Ihe sandy shore. In Ihe decomposing seaweed on Ihe 

 shore Ihe formation of CO.^ proceeds with still greater intensity. A 

 maximum of 2.tu mg. per 50 cm.'-^ in one hour was ohservcd here. 

 The seaweed, owing lo ils looseness, dampness, and abundance of 

 corrupting malier, must be regarded as an extremely suilable soil 

 for bacteria of various kinds (including sulphur bacleria). 



The values obtained refer to an air-lemperalure of 14 — 16'* in Ihe 

 forest and about 18" on the shore. The ground-temperalure was 

 not determined (and it varies, of course, with the depth). A more 

 detailed investigation of the CO.^ produclion will be underlaken 

 next year. For a preliminary estimate, however, the ligures given 

 furnish suflicient support. 



In the last column of the lable the values found are expressed 

 in mg. per 50 cm.'^ per 1 hour, in order lo facilitate a comparison 

 with the assimilation-values. Thus in the forest Ihere lakes place 

 a COo produclion of 0.84 — I.tö mg, (on an average about 1 mg.) per 

 50 cm^ in one hour and at an air-temperature of 15°. The curves 

 in fig. 2 show that 1 mg. of CO2 is consumed by a leaf-surface of 

 similar extent at a light-inlensity of about ■^^^, if the CO.^ concen- 

 traiion of the air is 0.f,i mg. per litre. Wilh higher CO,^ concen- 

 tration more is assimilated. Even during the lighter hours of the 

 day, therefore, a forest-plant needs little more carbon dioxide than 

 is produced by ihe piece of ground on which it stånds, and that 

 even if the assimilating leaf-surface is assumed lo be of e((ual size 

 with the piece of ground. 



In normally shaded parts of the förest Stellaria nemorum. Circea 

 alpina, etc show an extraordinarily beautiful leaf-mosaic. The assi- 

 milating leaf-mass is praclically reduced lo a single level. Ouly in 

 the lighter parts of the forest do the planls shoot up alofl and the 

 leaves form layers under one anolher, so that here the total assi- 

 milating surface is greater than the surface of the ground beneath 



