264 BOTANICAL GAZETTE [APRIL 
enced by that in photosynthesis, and it may logically be demon- 
strated as follows: 
Take three test tubes on feet (fig. 5) or their equivalent, and 
fill each half full of, respectively, (1) pure water, (2) strong 
caustic potash, (3) mixture of concentrated caustic potash and 
pyrogallic acid. Take three U-tubes of somewhat smaller diame- 
ter than the test tubes, and in one end of each place about 
twenty soaked fresh radish seeds, or else a few soaked oats, 
placing under each lot a wad of moist sphagnum, and shut 
them in by a tight rubber cork. The other ends of these tubes 
are to be placed in the three test tubes. It will be found after 
a few hours that the pyrogallic mixture had risen in the U-tube 
about one fifth of its length. This is because it has absorbed 
the oxygen, and it is the most convenient way to get rid of 
oxygen from a small space. These seeds do not germinate, 
or only very slightly (probably from intramolecular respiration, 
though possibly because not all of the oxygen has been removed). 
In the tube with the potash, in a day or two, the liquid has risen 
to about one fifth of the length of the U-tube, and the seeds 
have germinated. The rise is of course due to the absorpuos 
by the potash of the carbon dioxide given off by the germinating 
seeds. In the tube with the water the liquid rises bt. 
though the seeds germinate freely. This part of the experi 
is necessary in order to prove that it is not simply the wie 
tion of the oxygen that allows the liquid to rise in 10. * 
that an equivalent volume of another gas is given off. en 
This experiment logically proves, (1) that oxyge" § "() 
Sary to growth; (2) that oxygen is absorbed in age 
that carbon dioxide is given off in growth; (4) that ae 
absorbed and carbon dioxide given off in growth are A 
volume. Thus is respiration demonstrated. 
In setting up the pyrogallic tube it is prac 
place the pyrogallic acid in the end of the U-tube an 
centrated caustic potash in the test tube. U-tubes, 
Straight tubes with the seeds at the upper end, are bes 
n the latter case moisture runs down from the wets 
potash diffuses up the streams and kills the seeds. 
tically best 43 
d the con 
instead 
t, because 
eeds and 
