85 



place to place. Many of the troublesome qualities 

 which weeds possess are due indirectly to certain 

 characteristics of the seeds: (1) the enormous num- 

 ber produced by a single plant; (2) their remarkable 

 adaptations for dispersal; and (3) their wonderful 

 vitality. 



Productivity of weeds. A single plant of many 

 common weeds like the foxtail and the lamb's-quar- 

 ters may produce 25,000 seeds. It has been esti- 

 mated that a single plant of purslane may produce 

 100,000 seeds; of pigweed, 300,000; of lamb's-quar- 

 ters, 1,800,000; and of wormseed, 26,000,000. At 

 Ames,, Iowa, a square rod of ground in a garden, 

 which had been in potatoes the year before and cul- 

 tivated with a hoe, yielded 187,884 plants of eight 

 common weeds. 



Dispersal of weed seeds. The seeds of weeds are 

 well adapted for dispersal. Many are scattered by 

 the wind ; some of the tumble-weeds are rolled along 

 on the prairies; some have winglike attachments, 

 like the docks; others have hairlike appendages, like 

 the dandelions. Others have hooks by means of 

 which they may be attached to clothing and fur and 

 thus be carried long distances. 



Vitality of weed seeds. And then, finally, after 

 the seeds have reached then* resting-places, they may 

 retain their vitality and be able to germinate after 

 many years of exposure to winter cold and summer 

 drought. The seeds of most of our common weeds 



