1 84 AGRICULTURE 



mend an injury. Johnson grass is more easily killed in 

 August or September than earlier. In killing biennial or 

 perennial weeds, they must be cut off below the crown. 



Smothering weeds. Sometimes the farmer can hire 

 other plants to kill weeds. A crop of cowpeas or of 

 velvet beans will sometimes smother Bermuda grass so 

 that very little of it is left at the end of the season. The 

 cowpeas or velvet beans kill the grass by shading it and 

 by taking up the soil water which the grass needs. 



Keeping weeds off the farm. Good plowing and care- 

 ful preparation may greatly reduce the number of weeds 

 on the farm. But their seed or those of worse weeds may 

 be brought back mixed with purchased seed of grain, 

 clover, or grass. Weed seeds are sure to be present in the 

 cheaper grades of grass and clover seeds. It pays to buy 

 the best of these in spite of their extra cost. 



EXERCISE. Learn to recognize the seeds of some of the worst 

 weeds. A collection that is interesting and useful consists of small 

 bottles of weed seeds, properly labeled. 



NOTE TO THE TEACHER. Let pupils make a list of weeds of 

 which they can find the seeds and ask them to observe whether these 

 are spread by (i) wind, (2) adhering to men or animals, (3) by the 

 popping of the pods or seed cases, or (4) otherwise. If Bailey's 

 * Lessons with Plants" (Macmillan) is at hand, read pp. 336-341. 



FIG. 123. ONE OF THE TROUBLESOME MORNING-GLORIES 



