This fossilised tree fern comes from the Maranhao Sedimentary Basin in NE Brazil. It grew in the Permian period (late Palaozoic era) approximately 270 million years ago. Species is probably Tietea singularis or (less likely) Psaronius brasiliensis but I'll need to do more research before I can say with confidence.
This particular slice probably comes from near the base of the trunk/branch as it is almost entirely made of the central (supporting) stele. This is identifiable by the numerous brain-like structures of the vascular bundles of xylem tissue. The slice is polished on front and back and this posting includes images from both sides.
It's striking just how different the internal structure is from that of a tree.
I have another fossilised fern that shows the middle/upper trunk with cells that would have been involved with the transport of water and nutrients as well as the leaf bases. I'll do a project on that fossil for comparison with this posting sometime soon.
I will also pop this slice under the Meiji stereo microscope (maybe tomorrow) and will post results in the microscope forum.
Images are stacks of ~5 frames.
Bruce


