An epoch in the evolution of plants, proposed in 1993 by J. Gray, that lasted from the latest Llandovery (about 428.2 Ma ago) in the Early Silurian until the mid-Lochkovian (about 413 Ma ago) in the Early Devonian. During this epoch simple plant spores, dispersed individually, become increasingly common in several plant groups, including early vascular plants, and the earliest undoubted plant megafossils have been dated to this time.