Stomata and sterome in early land plants
by Edwards D., Fanning U., Richardson J. B. (1986)
In Nature 323: 438–440 –
Recognition of pioneering land plants in the fossil record is highly contentious. Because vascular plants possess numerous structural modifications which maintain an internally hydrated environment, attempts to demonstrate the vascular status of megafossils have traditionally dominated research, although more recently evidence from microfossils suggests that Ordovician and Silurian land vegetation may have included plants with some attributes of bryo-phytes1,2 and thallophytes3,4.
Silurian megafossils are preserved as impressions or coalified compressions5, in which anatomy is rarely preserved. The claim to land plant status of Ludlow and Pridoli examples of the presumed rhyniophytes Cooksonia and Salopella is based on their axial architecture, and hence presumed erect growth habit, and on their in situ spores with sporopollenin.
Here we report on exceptionally preserved coalified fossils from the basal Devonian of Shropshire which show that Cooksonia also possessed stomata and thick walled supporting tissues although evidence for vascular tissue still eludes us.