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 j)ond 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 I 

 water snails clinging to leaves and sticks. You may know i 

 them by their spiral shells. Some w411 be as small as pin- 

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

 eat green leaves, and especially algse. 



