Hollow straws in pairs
deutsche Version
    Aglaophyton fork section   
This picture of a cut and polished face of a Rhynie chert sample offers more than sections of equal size and shape near each other, nevertheless let us begin with this conspicuous feature.
From the rather similar aspect of the sections one can conclude that there were two parallel shoots of equal size
emerging from a common base like prongs of a fork. Their mode of degradation must have been inherited from that base since the similarity could hardly have been incidental.
The "hollow straw aspect" seen on either prong is often met with Aglaophyton. Here it apparently supports the assumption that this type of degradation had been predetermined or had formed in the live plant, and that the plant was able to live with most of the cortex tissue missing, provided that a circumferential ring of tissue and the central strand were still functioning.
As it seems, this ring and the central strand were actively protected against decay by unknown means. There are still unsolved problems concerning these rings.

Image: Cross-section of forked Aglaophyton, either prong with "hollow straw" aspect. Width 15mm.

The decay could have been brought about by some fungus spreading in the cortex tissue of the live plant. Deformation and beginning decay of cortex cells is seen in the separate section above. Hyphae of an aquatic fungus are faintly visible as thin dark lines or dots surrounded by whitish coatings, in the corner below left in this image. Two multiply coated hypha cross-sections appear as "eyes " in a pale funny face near the middle of this image.
The largely shrivelled and shrunken plant section left of the middle indicates that there must have been a quite different mode of decay, perhaps rotting of the dead plant which had not become a hollow straw.
Obviously the supply of dissolved silica had not been sufficient to form silica gel and finally chalzedony throughout. There were big and small pockets of water left. Some got distinct linings of whitish or pale silica gel turning into chalzedony. Finally, quartz crystals grew slowly in the remaining cavities below right and at several spots above.
Yellow or red stains of iron oxides had been deposited in some of the small cavities above. Apparently, iron salts and oxygen had not been there at the beginning, otherwise a yellow or red chert would have formed. Possibly the two components had entered into the water-filled cavities and into the crack later by diffusion and combined there into iron oxides.
Sample Rh2/230, Part 2 (39g),  found by S. Weiss  in 2014.

  H.-J. Weiss       2018

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