78 A TEXT-BOOK OF GRASSES 



this group belong the spear grasses, species of Aristida, 

 whose sharp fruits with the triple awns become a nuisance 

 or even a serious pest. These fruits and others such as 

 those of Hordeum and Sitanion work their way into the 

 nostrils and eyes of animals and into the wool of sheep, 

 or form hair-balls in the stomach. 



107. The seriously troublesome weeds in cultivated 

 soil are those possessing creeping rhizomes. There are 

 three species of grasses that belong in this category. They 

 are Bermuda-grass, Johnson-grass and quack-grass. 

 Bermuda-grass has already been mentioned (Par. 28). 

 In cultivated soil the rhizomes become large and vigorous 

 and the plant is usually known then as wire-grass. Ber- 

 muda is a common weed in corn and cotton fields through- 

 out the southern states. Johnson-grass is exceedingly 

 troublesome in the black soils of the southern states (Par. 

 49). Quack-grass is a bad weed in the humid region of 

 the northeastern states. It is also called quick-grass, 

 quitch-grass and couch-grass. 



These three species, like all weeds with rhizomes, 

 cannot be eradicated by pulling them up or by cultivation 

 unless all of the rhizomes are removed, since a single 

 piece of rhizome may give rise to a shoot. They may be 

 greatly reduced in this way, however. On a large scale 

 they may be kept in subjection by plowing and harrow- 

 ing out the rhizomes, after which they are burned or 

 removed or spread so as to be dried out by the sun. 

 Another general method for eradicating such weeds is to 

 smother them with a vigorous crop, such as grain or 

 alfalfa. Small patches may be attacked to advantage with 

 the hoe, cutting off all the green shoots. If this is done 

 frequently the rhizomes are exhausted of their vitality 

 and are unable to produce more shoots. 



