34 



HISTORY OF FARM 



THE PLANT LIFE OF THE STREAM 



The rapids 

 are by no means 

 destitute of life. 

 Given natural 

 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 o f 

 stones that every 

 flood brings 

 down upon them. 

 They must be 

 simply organized plants, that are not killed when their cell 

 masses are broken asimder. Such plants are the algae: and 

 these abound in the swiftest waters. They form a thin 

 strattim of vegetation covering the surfaces of rocks and tim- 

 bers. Its prevailing color is brown :noi green. Its dominant 

 plants are diatoms. These form a soft gelatinous very slip- 

 pery 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 

 supply for a host of animals dwelling in the stream bed with 

 them. 



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

 spicuous of these is Cladophora, which grows in soft trailing 

 masses of microscopic filament fringing the edges of stones in 



Fig. 12. Spray of river-weed (Potamogelon crispus) 

 from a drawing by Miss Emmeline Moore. 



