Aglaophyton epidermis outlined
deutsche Version

Delicate anatomical structures of fossil plants preserved in chert are often hardly seen unless the optical contrast is greatly enhanced by some peculiarity in the processes of decomposition and mineralisation. The quite uncommon aspect of the epidermis of Aglaophyton in this photograph may serve as a conspicuous example of such phenomena. (The common aspect of the epidermis with stoma in cross-section is seen in Rhynie Chert News 2.)
Aglaophyton epidermis pattern with stark contrast due to peculiar dark lining inside the cellsEpidermis pattern drawn for better visibility
Photograph: Slanting cut of Aglaophyton shoot with conspicuous surface pattern consisting of peculiar dark frames inside the epidermis cells.

Drawing: Pattern drawn for better visibility of the cell walls faintly seen there.

Apparently some dark substance is arranged such as to make a plane frame within every epidermis cell, fitting to the shape of the cell and keeping a rather even distance from the lateral cell walls.
The outer edges of the epidermis cells are faintly seen as thin lines forming a network of polygonal meshes right between the dark frames.

In some places where the frames have been cut, a tiny bright spot or line of reflected light is seen. This means that the polished chert face is not plane there. Hence one can conclude that the dark matter of unknown origin is mechanically different from the surrounding chalcedony.
The frames are enigmatic since usually there is not the slightest indication of such phenomenon on the surface of silicified plants in the Rhynie chert. (See Rhynie Chert News 47.)
No explanation is proposed here. Suggestions are welcome.

H.-J. Weiss
    2005,        emended 2013
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