167 



through the thermostat, whilst the other room contained 

 the nitrogen-cylinder, the two wash bottles and the com- 

 bustion furnace. 



The Arrangement (PI. XVII). 



The nitrogen first passed through the wash bottles with 

 pyrogallol and the furnace, after which the exit tube 

 entered the dark room through an opening in the wall. 

 The gas was first cooled by passing through a leaden 

 spiral, placed in a vessel of water and then passed through 

 the thermostat. The waste-pipe ended under water and 

 served as a control against leakage, because in that 

 case bubbling stopped at once. The nitrogen-cylinder 

 was always opened so far that the bubbles of gas succeeded 

 one an other at a constant rate. 



In those experiments in which fresh air was drawn 

 through the apparatus, the cube which led into the ther- 

 mostat was connected to a tube through which the outer 

 air could enter. Further the exit tube was attached to 

 an aspirator. 



Recueil des trav. bot. Néerl. Vol. XIV. 1917. 12 



