34 



NATURAL HISTORY OF THE FARM 



THK PLANT LIFE OF THE STREAM 



The rapids 

 are by no means 

 destitute of life. 

 Given natural 

 ^IV~^ i^ Py r^^ 1^ waters, a tem- 



perature above 

 freezing, light 

 and air, plants 

 will grow any- 

 where : here, 

 they must be 

 such plants as 

 can withstand 

 the shower of 

 stones that every 

 flood brings 

 down upon them. 

 They must be 

 simpl>- Drganized j^lants, that are not killed when their cell 

 masses are broken asunder. Such plants are the algae ; and 

 these abound in the swiftest waters. They form a thin 

 stratum of vegetation covering the surfaces of rocks and tim- 

 bers. Its prevaiHng color is brown, not green. Its dominant 

 plants are diatoms. These form a soft, gelatinous, and xoxy 

 slippery coating over the stones. Individually they are too 

 small to be recognized without a microscope, but collec- 

 tively, by reason of their nutritive value and their rapid 

 rate of increase, they constitute the fundamental forage 

 sui iply for a host of animals dwelling in the stream bed with 

 them. 



There are green algec also in the rapids. The most con- 

 si)icuous of these is Cladophora, which grows in soft trailing 

 masses of microscopic filaments, fringing the edges of stones in 



Fig. 12. Spray of riverweed (Potamogeton crispus) 

 Frnm a drawing by Miss Emmcline Moore. 



