SEED DISPERSAL OF WEEDS 



103 



cork-like coverings and float long distances in streams. Birds 

 eat some seeds and scatter them undigested, far from the parent 

 plants. A study by some school children showed that common 

 weeds given a start in one place might within three years, under 

 average conditions, spread from an area four acres to over three 

 hundred acres in extent around the point where they first came up. 

 Why not make a study in your home locality to determine the 

 rate of spread of some weed? 



Wright Pierce 



The Russian thistle, a tumbleweed, breaks loose when dry and is blown about by the wind, 

 scattering its seeds as it rolls along. 



Laboratory Exercise. Select a common weed in your community, 

 and bring it into the laboratory. Thrash out the seeds. Collect and 

 count the seeds and estimate a possible total number of seeds which 

 may be scattered over a given area by several hundred weeds. 



Weeds have great vitality. Those of us who have tried to get 

 rid of weeds from a garden or from the lawn know some of the 

 devices these pests have to maintain themselves : long and tough 

 roots and stems ; roots which develop wherever the stem touches 

 the ground; leaves protected by thorns or hairs; roots which 



