With thanks to H.-J. Weiss who gave me the sample of Rhyniechert. I, the copyright holder of this work, hereby publish it under the following licenses:
Attribution-Share Alike 4.0 truetrue English Superficial view of a ''Rhynia'' stem with scale bar added URL: https://commons.wikimedia.org/wiki/user:Peter_coxhead
Commons Attribution-Share Alike 4.0 truetrue English Superficial view of a ''Rhynia'' stem object of statement has role: photographer author name string: Peter