246 ARID AGRICULTURE. 



most desirable. Weeds make the poor farmer a 

 nuisance to the whole community, for his crop of 

 weeds is a blighting pest sent to do his neighbor 

 harm. If a farmer choose an unprofitable hus- 

 bandry, it is his own folly; but if that system 

 harms his friends, he should be summarily dealt 

 with in proportion to the offense. A quarantine 

 against weeds, especially where we have winds 

 and running irrigation water to facilitate their 

 spread, is as reasonable as any other quarantine. 

 Some weeds poison our animals or ourselves. 

 The milk weed, known as "Snow on the moun- 

 tain," a native of parts of the West, is very pois- 

 onous to some persons, causing serious skin dis- 

 ease by simply touching it. Its beauty has 

 caused this weed to be planted and picked 

 for bouquets ; but people should understand its 

 nature and be on their guard. Almost every one 

 is familiar with the effect produced by the poi- 

 son sumac, poison ivy, or poison oak. Some- 

 times people attempt to eat weeds they know 

 nothing about, like strange toad stools or the 

 wild peas which grow on astragalus plants in the 

 West, and if they happen to live, they always 

 have something to look back upon with regret. 

 The principal weeds that poison live stock are 

 discussed in Part VI, of this book. 



Some weeds are parasitic and injure or de- 

 stroy crop plants by living off their sap. It 

 would not be out of place to call the lower forms 

 of plants, which produce certain plant and ani- 



