ARABLE WEEDS. ASSOCIATION WITH SOILS 143 



really not very common. When it does occur, it is often 

 present in abundance, especially on sand. It is very rarely 

 seen on any soil heavier than gravel. 



Small nettle (Urtica urens) is another weed that is more 



often seen on sand than elsewhere, but never on chalk. It is 

 not of frequent occurrence, and it is very often scarce, so that 

 it plays little part in the general weed economy. 



Sheep's sorrel (Rumex acetoselta) (Fig. 38) is common on 

 all the lighter soils, though it has some preference for sand. 

 This may be one of the cases in which the lime deficiency has 



