51 



and is in aii-lighl isolation from llie assimilalion-chaniher. Tlic fasle- 

 ning ollhe objecl on lo Ihe rod can be perlornied whcn the cliamher is 

 eilher open or closed. In Ihe former case the rod siionld be in Ihc 

 position I. In the latter case it is drawn out to the position II. Tlic 

 outer stopper is then loosened and allowed to slip out to the handle, 

 III. The leaf is attached to the rod and piished into the luhe. 

 whereupon the stopi)er (r.,) is restored to its i)lace. The witluirawal 

 orinsertion of the ohjeet from or into the closed assimihition-chamber 

 has the great advanlage Ihat immediately after the conclusion of one 

 experiment another can be begun with the same leaf in anolher 

 chamber. If the stopper r.^ is provided with two tubcs, air can be 

 sucked Ihrough the glass tube and thus the respiration carbon dioxide 

 produced by the leaf may be got rid of, and if necessary measured, 

 immediately before or after an assimilation experiment. The inner 

 stopper should then of course be drawn out (positions II and III). 



The estimation of the carbon dioxide is performed by the in- 

 troduction of a certain quantity of diluted baryta solution into the 

 bottom of the assimilation chamber by means of a glass bowl (b) 

 secured with paraffin. Through tube T is introduced a glass tube 

 /, of equal calibre, reaching down to the bottom of the bowl. The 

 tube is closed on the outside by a short indiarubber tube and a 

 glass stopper. The liaryta is sucked from a vessel of supply into 

 a pipette of lö ccm. capacity, which is introduced into the mouth 

 of tube T, and then the baryta is allowed to run into the bowl and 

 spread itself uniformly över the bottom. Afterwards the tube is 

 closed, and the whole is left to stånd as long as is necessary for 

 complete absorption (with ^"^ baryta and normal carbon dioxide per- 

 centage in the air, at least half an hour). 



Then the baryta is sucked out inlo a small wide-necked llask of 

 50 — 100 ccm. capacity (IV). A quantity of waler free of CO.^ is 

 introduced through tube T, and the bowl is rinsed out by gentle 

 shaking of the apparatus. The rinsing-water is sucked up into the 

 same llask as the baryta, the process is repeated once or twice, and 

 litration then takes place directly into the llask with ^^ oxalic acid. 



The filling of the apparatus with ordinary air is most easily 

 elTected by letting it stånd in the open air for some minutes, with 

 the lid off, preferably in a windy place. The Kcological Station 

 ofTers ideal conditions in regard to fresh and constantly circulating 

 air. As the composition of the air by the sea remains very nearly 

 constant as long as the same wind is blowing, I only bad to make 



