Previous studies on Upper Carboniferous floral palaeoecology are reviewed and relationships between fossil plant assemblages, depositional environments, and contemporaneous plant communities are discussed. A point-quadrat sampling technique was applied to a quantitative study of plant horizons in a 'roof shale' of a thin coal beloe Skipsey's Marine Band (Westphalian B) at a locality near Annbank, Strathclyde. This study has shown that the number and percentage cover of 'drifted' and in situ species varies up the succession. Changes in the depositional environment from swampy flood plain to near channel alluvial discharge, interpreted from the lithofacies, are thought to account for these differences by affecting the quantity of plant material deposited and by incorporating a variety of Plant Communities to yield different fossil plant assemblages. The latter consist of two main types, one of pteridosperms with some Cordaites, and another of sphenopsids and pteridosperms with Cordaites. Only very few lycopod remains were found. This is in contrast to the coal-forming swamp community (as seen in the spores contained in the coal) which was dominated by lycopods with some sphenopsids.