Weed communities of British arable land have been extensively surveyed and classified using Zurich-Montpellier ("Braun-Blanquet") methods of analysis. After comparison of British results with continental literature it is concluded that most stands are referable to the class Stellarietea. A number of associations can be distinguished, classified as follows: Order: Polygono – Chenopodietalia Alliance: Fumario – Euhorbion Five associations Alliance: Spergulo – Oxalidion Seven associations Order: Eragrostietalia Alliance: Panico – Setarion One association Order: Centauretalja cyani Alliance: Arnoseridion Two associations Alliance: Aphanion Two associations Alliance: Caucalidion Three associations. Other communities of undefined rank have also been distinguished. Three new associations are provisionally described within the Spergulo-Oxalidion. Additionally, it has been found that some arable stands are referable to syntaxa of the classes Agroyretea or Plantainetea. Such stands are related to the effects of soil deterioration and selective herbicides. Limited investigation of annual communities of other disturbed ruderal habitats has shown that they are usually referable to the order Sisymbrietalia of the Stellarietea. Association between species has been investigated in some areas by chi-squared analysis. Plexus diagrams showing inter-specificassociation have been prepared for the Outer Hebrides, Dorset, the Isles of Scilly, the Brecklands, the Lower Greensand plus Bagshot Sands formations and arable bryophyte synusiae. Results from these are compared with those of the Zurich-Montpellier analysis. Factors affecting arable communities are extensively reviewed. Special consideration has been given to the floristic and ecological nature of the field boundary
