ARABLE WEEDS. ASSOCIATION WITH CROPS 165 



(b) Weeds Discouraged by Root Crops. 



TABLE XI. WEEDS DISCOURAGED BY ROOT CROPS. 



Very few of those weeds thus discouraged are present 

 in large quantities under any circumstances, and this may 

 account for the comparative ease with which they are re- 

 duced among roots. Pimpernel (Anagallis arvensis'), mouse- 

 ear chickweed (Cerastium vulgatum), and dwarf spurge 

 (Euphorbia exigua) have never been found dominant anywhere, 

 while greater plantain (Plantago major), creeping buttercup 

 (Ranunculus repens], field pansy ( Viola tricolor], campion 

 (Lychnis vespertina) have each one record of dominance to 

 their credit among other crops, but never one among roots. 

 The red poppy (Papaver rhceas), however, provides a single 

 example of a weed that is most abundant in some districts, 

 and yet often absent from the root crops in these very 

 areas. The soil contains numberless seeds, but under these 

 particular conditions of cultivation the poppies make little head- 

 way. This is well shown by the fact that the red poppy was 

 only once found dominant amongst roots, when among other 

 crops in the same district it dominated no less than 92 

 times. This fact in itself shows how bitterly the poppy 

 resents the interference of cultivation. White mustard (Bras- 

 alba) behaves in a similar way, though the discrepancy 



