128 DUCKWEED 



are the stems of most plants that grow in swiftly running 

 water ? 



Pond Algae. Wherever you find duckweed growing, you 

 will also be likely to see a green scum floating on the water 

 and covering sticks and stones with waving tufts. This is a 

 kind of pond alga. Take some in your hand, and see of what 

 it is made. Do you see separate threads as fine as the finest 

 silk ? Examine some of the threads with a microscope. Do 

 you see beautiful spirals of green running along each thread ? 



Snails. .Along with duckweed you are quite likely to find 

 water snails clinging to leaves and sticks. You may know 

 them by their spiral shells. Some will be as small as pin- 

 heads, and you may see others as large as your thumb. They 

 eat green leaves, and especially algae. 



