140 A MANUAL OF FARM GRASSES 



the water courses. Forested valleys are classified with 

 humid forests. The valleys support a richer vegetation 

 because of the greater fertility of the soil and because of 

 the greater water supply. They are usually the first 

 part of a region to be occupied by habitation and are the 

 first to be turned from grazing to field crops. Up to the 

 present time, an important part of the grazing areas of 

 the arid and semiarid regions has been supplied by the 

 valleys. Since they contain the chief water supply, the 

 valleys were taken up as claims and are now mostly 

 under private ownership, hence are usually fenced. In 

 so far as these pastures contain the original native vege- 

 tation they may be discussed under the subject of ranges. 

 In this discussion will be included both pasture and 

 meadow grasses. In the valleys the richer growth is 

 utilized for the production of hay. The grasses of the 

 valleys are, in the main, different from those of the 

 uplands. The original vegetation has often been in- 

 creased and sometimes considerably modified by irri- 

 gation or flooding. The unwonted water supply has 

 encouraged the growth of those species that are accus- 

 tomed to moist soil so that sometimes these species have 

 become dominant over large areas. Unfortunately 

 these moisture-loving species may be of inferior forage 

 value. A notable case of this kind is the so-called wire 

 grass of the Rocky Mountain region. This is a species of 

 rush {Juncus balticus L.) and not a true grass. It is 

 now the dominant plant in many parts of Wyoming and 

 adjacent states, where it is the custom to flood the native 

 meadows. The excessive water supply has encouraged 

 the growth of the wire grass and has inhibited the growth 



