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. 
