188 SOUTH AFRICAN BOTANY 
carbon di-oxide in the first jar and replaced it by oxygen, 
otherwise the taper would be extinguished, as it is in 
the second jar. 
107. Experiment 15.—To see if water plants give out 
oxygen. 
Apparatus.—Slips of Elodea, or some other water 
weed, funnel, large beaker, test-tube. 
Method.—Fill the beaker with water, and fix the 
water weeds under the funnel in it. Fill a test-tube 
Fic. 76.—Experiment 14.—a. When Candle is Burning; 6. Candle 
Extinguished. Note the rise in level of the water. 
with water, place your thumb on the end and in- 
vert it into the beaker of water. Slip it over the top 
of the funnel (which must be under water), taking care 
that no water runs out. Place the apparatus in sun- 
light. 
Observations.—Bubbles arise from the weeds and go 
up to the top of the test-tube, gradually displacing the 
water. When the tube is nearly full of this gas shp 
it off the funnel, keeping the mouth under water, put 
your thumb under the end as before, and take it out. 
Keep the tube closed till you are ready to test the gas. 
