378 WEEDS 



the time the seed case ripens. This is typical of a number of others. 

 The carrying of seeds on the coats of animals has been mentioned 

 and illustrated, and numerous examples are everywhere found. 

 Wind is an important factor in the spread of seed "flying machines." 

 The dandelion, thistle and milk weed seeds are carried long dis- 

 tances in high winds. Certain seeds are carried on the water and 

 may be left in inundated fields, or along the banks of streams. 

 Edible seeds are carried by birds, squirrels and other animals, and 

 a large proportion of them are left in places where they may grow. 

 The almost incredible number of seeds produced by single plants 

 plays an important part in the problem of weed dissemination. 



Commercial Operations Spread Weeds. A number of the 

 worst weeds in America have been introduced from the Old World 

 through the use of packing material containing weed seeds. In 

 like manner eastern weeds have been sent to the western states. 

 The shipment of grains, stock feeds, hay, straw and similar mate- 

 rials from one part of the country to another will spread the weed 

 seed which may chance to exist therein. 



Farm Practices Spread Weeds. Farmers who buy their feeds 

 raised in distant places will find that manure when spread on their 

 own fields is infested with new forms of weeds, and from this field 

 or farm the weeds may spread to the neighboring fields. 



Thrashing machines become infested with weed seeds on one 

 farm and from there they go to other places where the seed is blown 

 out and finds congenial soil on which to produce a new crop. 

 Manure is hauled from the cities to the country. City stables 

 may have been using feeds, bedding or roughage from distant 

 places, the manure is full of the seeds and the farmer plants them 

 when he spreads the manure. This is one of the strongest argu- 

 ments used by gardeners against the use of stable manure and in 

 favor of commercial fertilizers, 



It is a far too common practice to allow weeds to go to seed along 

 fence-rows, roadsides and other waste places. From here many 

 fields are badly infested. 



Tillage implements such as harrows and cultivators will often 

 carry parts of weeds or their seeds from one part of the farm to 

 another. This is particularly true with such weeds as those having 

 long rootstalks as Canada thistle, quack grass and Johnson grass. 



Foul seeds purchased from dealers or from farmers are among the 

 sources of weed infection. Growers cannot be too careful in selecting 

 clean seed, and avoiding the use of seeds grown in places where noxi- 



