A DEMONSTRATION OF PHOTOSYNTHESIS 
107 
internal diameter. A ring (W) is fastened firmly against the stopper 
so that the stand may be inverted without displacing any part of the 
apparatus. 
The procedure is as follows: We place vigorous plants^ (covered 
with young leaves capable of active photosynthesis) in the bottle and 
fill it with water to about one tenth of its capacity. The stopper is 
then inserted. If provision has been made for three long tubes only 
one of them is now attached. One of the short tubes which perforate 
the stopper is connected to a C02-generator2 (this tube is first clamped 
off). The other short tube is connected to a piece of glass tubing of 
small diameter. 
The apparatus is now inverted, allowing the long tube to fill with 
water. Sufficient CO2 is now admitted to drive out most of the water 
from the bottle through the narrow tube.^ The apparatus is now 
returned to the upright position and the two remaining long tubes 
are connected to the bottle. 
The apparatus is now inverted, allowing each of the long tubes to 
become partially filled with water. On placing in an upright position 
the water runs back into the bottle. This is repeated until the gases 
are well mixed and the water is nearly in equilibrium with them. 
In case it is desirable to protect the leaf from wetting during the 
inversion of the apparatus the plant may be tied to a vertical support 
(passing downward through the center of the stopper) in such fashion 
that it does not touch the sides of the bottle. 
By inverting the apparatus just enough water is allowed to run 
into one of the tubes, A, so that when in the upright position the 
water level can be seen above U. The tube A is then closed by two 
clamps, U and V. The apparatus is placed upright and the tube A 
is removed by cutting the rubber tubing below U or by slipping it off 
from S. This allows the removal of A without admitting air to A or 
to the bottle (the tube A being closed by the clamp U and the tube 
R by the clamp F). 
1 Tradescantia may be recommended for this purpose, especially kinds with non- 
striped leaves. 
2 The CO2 must be well washed on its way to the bottle. 
3 Another procedure is to put into the bottle only enough water to fill two long 
tubes. Keeping the apparatus upright, run in CO2 allowing it to displace air which 
issues through another short tube and is collected in an inverted graduate filled with 
water and dipping into water. When air representing about one tenth of the capacity 
of the bottle has been displaced by CO2 the long tubes are put into place. 
