CHAPTER XVI 
THE WORK DONE BY PLANTS IN MAKING STARCH 
Plants do work. It seems strange that plants work; 
yet it is quite true. Some plants do a great deal of 
work, and hard work too. Plants work when they 
make starch, though, as we have seen, they cannot do 
this work without the help of light. But light, with- 
out the leaf-green and the living plant, cannot make 
starch. We cannot see the work which the green 
plant does, but it 1s easy to see some of the signs which 
tell that the work is going on. We must learn to read 
the sign language. 
How water plants tell of this work. Let us select 
some water weeds, or leafy plants which grow in ponds, 
lakes, or streams. A very good plant for this purpose 
is the elodea, but when this cannot be found others 
may be obtained which will serve quite as well. The 
plants may be brought to the room and placed in a 
bottle of water which is set in the window, so that they 
will get the sunlight, or the brightest light which may 
be had if the day is cloudy. In a very short time 
bubbles of gas collect on the leaves, small ones at first, 
but increasing in size until they are freed. Then they 
115 
