419 



<i. the decrease of |)i'es,siu-e and oxygeii-ooiiteiit in the a|)|)aiatns 

 is reduced to a mini inn in. 



h. tiie place of the oonsiiined 0, is at once taken by pure 0,, 

 witiiont first passing a stop-valve, and may directly be controled. 



c. an oxygen-bomb or other reservoir may be omitted. 



Fig. 7. 



The apparatns has been constructed by Mr. P. A. dk, Bouteh, 

 amannensis at the Botanical Laboratory at Utrecht. I am greatly 

 indebted to him, not only for the way, in which he performed his 

 task, bnt also for introdncing some clever improvements. 



Utrecht, May 1923. Botanical Laboratory. 



