154 WEEDS 



some of which disappear rather rapidly, while others appear to 

 thrive as a result of cultivation, and are a continual source of 

 annoyance. But the number of different kinds of weeds will 

 increase. Man will naturally introduce the grains, grasses, 

 clovers and vegetables that he believes can be grown advantage- 

 ously and more or less weed seeds will be introduced with 

 them. Some of these weeds will grow for a single season and 

 die while others will persist from year to year. Other weed 

 seeds will be carried with nursery stock and on the feet and in 

 the hair of live stock, in bedding for live stock, in feeds and 

 in packing materials and in many other ways. In many local- 

 ities stable manure is shipped from the cities to the farms and 

 since the animals from which it is secured may have been fed 

 on imported feeds and bedded with materials brought from a 

 considerable distance we can easily understand how great quan- 

 tities of weed seeds can be introduced. 



Fighting Weeds. Every grower of farm crops must make 

 a continuous fight against weed pests. In doing this there are 

 two general methods to follow: (1) Prevent the introduction of 

 the weeds not already present on the farm, and (2) the destruc- 

 tion of those that are present. 



Prevent Introduction. The introduction of many weed 

 pests can be prevented by using nothing but clean seeds. Many 

 seeds, especially clover and grass seeds, frequently carry many 

 weed seeds. The examination of an ounce or more of such 

 seed will frequently reveal the presence of many seeds of trou- 

 blesome weeds. Unfortunately, the seeds of some plants are so 

 similar to certain clover and alfalfa seeds that they cannot 

 be detected by persons unfamiliar with their minor character- 

 istics. The Federal government and most of the State gov- 

 ernments employ seed analysts who make examination of sam- 

 ples which are sent to them. Home-grown seed should be just 

 as carefully examined as seeds that are purchased on the mar- 

 ket. (Figs. 95 and 96.) 



