

116 THE WORK OF PLANTS 
rise to the surface of the water. Some of the plants 
should be placed in an inverted position in the bottle so 
that the cut end of the shoot will be below the surface. 
From this cut end of the shoot bubbles 
of the gas come out more rapidly than 
from the leaves. Most of the gas, it 
is true, came from the leaves, but 
there are air spaces all through the 
plant between the cells, so that the 
gas which is formed in the leaves can 
pass out not only at tiny openings in — 
the leaf, but also through the connect- 
ing spaces in the stems. 
The more light there is the faster 
the work goes on. If the bottles con- 
taining these water plants are kept in 
the window for several days, and there 

is cloudy weather as well as sunshine, 
ness you will notice that the bubbles of gas 
ae come out more rapidly on a sunshiny 
day than on a cloudy one. The more light there 1s, 
then, the more work the plant can do. This can be 
told in another way. Remove the bottle from the wih- 
dow and put it in a poorly lighted corner of the room. 
The gas is given off more slowly. Cover the bottle 
with dark cloth to shut out all light. In ten or fifteen 
minutes uncover it. The escape of the gas has ceased. 
