20. 



crop. The above treatment can only be recommended for an- 

 nuals. Many of the seeds of weeds will germinate but some will 

 keep their vitality for some years as sweet clover and Indian 

 mallow or butter print. The seeds of both weeds are known to 

 keep their vitality for more than half a century. 

 Perennial Weeds. The above methods will only partially destroy 

 the perennial weeds. Quack grass, Canada thistle, and weeds 

 of this character need special treatment. If the leaves of these 

 perennial weeds are prevented from growing the weed will be 

 killed in the course of time, they will starve usually, however, in 

 ordinary methods of cultivation, but some plants are not noticed 

 and these give rise to new plants. Let me give a few weeds with 

 specific treatment. 



Quack Grass (Agropyron repens). Creeping rootstocks and a number of 

 stems (culms), a spikelet at a., each containing a number of flowers, o a 

 spikelet with sterile glumes at 2 and flowers above. 



