188 
easily elapse before the analysis is made, a time whicli is more 
than sufficient for an utter alteration of the composition of the 
air to take place (the cause of this of course being the respiration 
of the plant). 
In order to find out whether it miglit be better to bring the 
roots home quite exposed to the air, I made after having been 
enabled to carry out analyses on the spot the two following analyses: 
°lo 0 2 
°/o C0 2 
Air from the rhizoma of Nuphar lutea. Analysed 
9 16 a. m. . 
6,3 
6,3 
Analysis of the same rhizoma li 40 a. m. after having 
been exposed to the air 2 hours 25 min. 
20,5 
0,3 
This shows plainly the absolute necessity of making the analyses 
on the spot. The following have therefore all been made in a 
boat by means of the portable apparatus. In this way at most 
15 minutes will elapse (for instance when two analyses on the 
same plant are wanted). 
When the plant, however, is kept floating on the water with 
its roots submerged, a state which as nearly as possible corresponds 
to the natural condition, no particular alteration will take place as 
the following analyses show. 
12 h 1914. Analysis of the intercellular air from a 
Nuphar root. 10,2 °/o 0 2 . 
— Analyses of the air from the corresponding 
spot on a neighbouring root made 2 hours 
after the foregoing, during which interval 
the plant was floating on the water with 
submerged roots. 9,7 °/o 0 2 . 
Even when a plant has been kept floating for a day in 
this manner no appreciable alteration will take place. 
