Article: The stratigraphic occurrence of early land plants
Determination of the age of the first land plants depends on sequences established for marine animals and possibly plant spores. Cooksonia in the Downtonian of Wales is currently the oldest proven vascular plant macrofossil. Similar appearing plants are found in comparable deposits in Czechoslovakia, U.S.S.R. (Podolia), and the U.S.A. (New York). The vascular nature of older macrofossils is unproven. The considerable evidence of older spores could be interpreted to mean that the separate characters of vascular plants evolved independently. Gedinnian and Lower Siegenian vascular plants differ little from Silurian ones but mid-Siegenian saw the beginning of a marked increase in kinds of vascular plants.