SCATTERING OP WEEDS 



637 



Fig. 501. Birds scatter the seeds of the Wild Black CJierry (Prunus serotma). 

 1, flowering branch ; 2, fruit ; 3, fruiting branch ; 4, cross section of fruit ; 

 5, flower; 6, branch with buds. 



(After Cheney in Green's Forestry of Minn.) 



From an ecological point of \dew weeds are plants which adapt 

 themselves readily to ordinary agricultural conditions and since 

 most crops are grown under mesophytic conditions, most weeds 

 are mesophytes which adapt themselves to definite habitat con- 

 ditions such as cultivated field or uncultivated field and are readily 

 transferred with agricultural seeds, hence the association of certain 

 weeds exclusively with certain crops, for example, among the com- 

 mon clover field weeds are buckhorn, wild carrot and plantain. 

 These are not found in corn fields where eocklebiar, horse nettle, 

 morning-glory and sandbur flourish. Many of the most obnoxious 



