Small, relatively uncompressed, very fragmentary plant remains (mesofossils) are described from a Silurian (Pridoli) and a Lower Devonian (Lochkovian) locality in the Welsh Borderland. Excellent cellular preservation provides characters leading to the demonstration of diversity in plants of simple gross morphology and allows deliberations on functional anatomy (e.g. of stomata), and reproductive biology (including development and dehiscence of sporangia). A survey of in-situ spores is presented, and preliminary comparisons made with dispersed spore assemblages especially in relation to reconstruction of vegetation on local and regional scales. The earliest body fossils of unequivocal terrestrial arthropods isolated from the same locality as the Pridoli plants suggest that the decomposer/microherbivore/predator soil and litter communities found in the Lower and Middle Devonian extend back at least into the Silurian. Evidence for plant-animal interaction in the Lower Devonian comes from spore-dominated coprolites believed to have been produced by litter-feeding myriapods.