ARABLE WEEDS. ASSOCIATION WITH SOILS 155 



any type of calcareous land, whether chalk, chalky loam, 

 chalky sand, or red land. 



In a few cases the differences between the three tables are 

 possibly caused by the local distribution of certain weeds. If 

 plants are at all localised it is quite likely that utterly different 

 results may be obtained by various workers or by the same 

 worker in different areas. As an instance of this, Scandix pecten 

 {shepherd's needle) may be cited. In Wiltshire, in 1911, this 

 plant was almost exclusively associated with chalk and red 

 land, and it occurred frequently enough to be considered a 

 chalk lover. In Norfolk, in 1912, and in Notts and Derby 

 in 1915 the same species was not once seen on chalk, and 

 only very rarely on chalky loam, so that it behaved practically 

 as a calcifuge. In Bedfordshire, in 1910, it was not often 

 seen, but it was associated with several kinds of soil without 

 showing much preference. This at once shows how the 

 difference may have arisen between Long's and the writer's 

 observations on this species, and also affords an indication 

 that if more data were forthcoming many of the other differ- 

 ences would be modified or eliminated. 



