ARABLE WEEDS. ASSOCIATION WITH SOILS 129 



Nepeta glechoma 

 Potentilla reptans . 



* Prunella vulgaris . 



* Ranunculus bulbosus 



* Sisymbrium officinale 

 Urtica dioica 



Ground ivy. 

 Cinquefoil. 

 Selfheal. 



Bulbous buttercup. 

 Hedge mustard. 

 Stinging nettle. 



The weeds marked * were very often scarce, and it is. 

 noticeable that they are all characteristic of grass-lands or 

 hedges, and are not commonly associated with arable land. 

 In no single case did any weed in this list attain a position of 

 dominance. 



Thalecress (Arabis thaliana) may perhaps be included 

 here though it was only seen three times, on three different 

 types of soil, in Bedfordshire. Arable land is a very unusual 

 habitat for this species, it being a frequenter of old walls and 

 waste stony places and not usually appearing on cultivated soil. 



(b) Plants Occurring on all Soils, but less Frequently on 

 Heavy Land. A small number of the weeds that are of general 

 distribution are much less common on heavy loams and clays 

 than they are on the lighter soils, on which as a rule they 

 are fairly evenly distributed. The number of species that come 

 under this heading is very restricted, as usually the weeds that 

 are scarce on the heavy land show some definite preference for 

 a particular type of soil, such as sand or chalk, which does not 

 occur in this case. 



TABLE II. WEEDS OF GENERAL OCCURRENCE, BUT LESS FREQUENT 



ON HEAVY LAND. 



The common red poppy (Papaver rhoeas} is so very wide- 

 spread and abundant that in some districts it is one of the 

 most difficult weeds to fight. It is popularly believed to 

 be peculiarly a weed of sand and very light soils, but close 



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