Diverse anatomically preserved plant assemblages occur abundantly in Lower Carboniferous volcanic sequences in the Midland Valley Basin, Scotland. They are preserved as calcareous permineralizations and as fusain (fossil charcoal). The plants occur in basaltic ashes, lavas, peats, and limestones. Many of the assemblages occur in deposits that are interpreted as products of phreatomagmatic activity. Numerous genera and species occur specifically in volcanic rocks. The volcanic activity may have stimulated the diversification of early ferns and pteridosperms in particular, as well as causing ecological disturbance and vegetational change.