138 WEEDS OF FARM LAND 



but on sand and light loam a better clearance can be effected. 

 It is often said that the presence of coltsfoot indicates an 

 easily available supply of underground water, or a high water 

 table, but definite confirmation of this statement is wanting 

 The plant is often one of the first to colonise newly made 

 dumps, railway embankments and similar "made" soils in 

 which the water supply tends to be deficient rather than 

 liberal and in which the water table or available underground 

 water lies at a considerable distance below the surface. It also 

 comes in when the nitrogen content of the soil is reduced, as 

 on the unmanured plot and that receiving minerals only on the 

 Broadbalk field at Rothamsted. 



Goosegrass (Galium aparine} is very widespread, but 

 shows as strong a preference for heavy land as coltsfoot does. 

 As an arable weed, however, it is less plentiful in quantity 

 and is often scarce on all kinds of soil, especially light land, 

 though it usually occurs in appreciable quantity on chalk. It 

 is seldom dominant in comparison with its frequency of oc- 

 currence, but this dominance is distributed over all soils and is 

 not confined to heavy land. 



Couch-grass (Agropyron repens) is regarded in many districts 

 as one of the most pestilential of weeds. Every small portion 

 of its rhizome is capable of originating a new plant, and even 

 with the most careful cultivation it is difficult to avoid 

 scattering the pieces broadcast. Consequently, couch-grass is 

 very often dominant, on any type of soil, although in its occur- 

 rence it seems to show a definite preference for heavy land. 

 It is quite possible that this preference is not a true one, and 

 this is supported by the frequent dominance on sand. On 

 light soil it is comparatively easy to scuffle out the creep- 

 ing rhizomes without breaking them, and so destroy them 

 wholesale. This cannot be done on heavy land, as every 

 attempt at removal breaks the rhizome and leaves innumer- 

 able fresh starting-points for the weed in the soil. Conse- 

 quently it may well be that couch-grass is in reality cosmo- 

 politan as to soil, but that methods of cultivation have given 

 it a false appearance of preferring heavy land. 



Dwarf spurge (Euphorbia exigua) is one of the less 

 abundant weeds which makes no important contribution to 

 the economy of the weed flora, although it is of frequent 

 occurrence. The preference for heavy land is very strong, 

 and it has a marked objection to sand and gravel. It is 

 never the chief weed, but on one occasion, at Inglescombe, near 



