CHAPTER XII. 



GKASSES USEFUL BUT DIFFICULT OF ERADICATION. 



In this chapter three grasses will be discussed which 

 are now almost universally looked upon as weeds. These 

 are Quack grass (Agropyrum repens)^ Johnson grass 

 (Sorglium halapense) and Crab grass (Panicum San- 

 guinale). All three are possessed of much economic 

 value and yet they are so difficult of eradication that 

 they have become in a sense the dread of the farmers in 

 localities into which they have been introduced. In 

 the judgment of the author, they should never be sown 

 on land that is to be tilled again. However, there are 

 localities where they have become so entrenched that 

 it may be the part of wisdom so to manage them that 

 the highest return possible will be secured, rather than 

 going to the expense of eradicating them. In other in- 

 stances and generally they should be given no rest by 

 those who cultivate 'the soil until eradication is com- 

 plete. In the hope that some light may be thrown 

 upon the difficult and perplexing problem of dealing 

 with these in a manner at once intelligent and effective, 

 these grasses will be considered separately and with 

 some minuteness. 



QUACK GRASS. 



Quack grass (Triiicum or agropyrum re pens) is prob- 

 ably more frequently designated Couch grass by those 



