Nematoplexus branch knot close-up
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Nematoplexus with black knot
The so-called branch knots related to Nematoplexus in a still obscure way have been considered in a previous contribution with several examples, among them rare big ones:
Rhynie Chert News 126. Another one of the more common type will be presented here with higher magnification (Figs.1,2).

Fig.1:  Nematoplexus: sparsely scattered tube fragments with right-handed thread, dark branch knot apparently detached.
Image width 1mm.

The pale or dark fragments of wound tubes in Fig.1 (tube diameter about 12Ám, thread diameter 100-130Ám) fit well into the majority of the tubes compiled in the diagram of spiral tube sizes 
in Rhynie Chert News 122.
Most conspicuous are the different tube sizes apparent in Fig.2. One tube of 12Ám had been torn off so that only a stump is left below right. A tube of the same size is very faintly seen in the corner above right and only slightly more distinctly in Fig.1.

Fig.2: Nematoplexus branch knot from Fig.1, showing largely differing tube diameters. Image width 0.15mm. Photograph by Gerd Schmahl.

Nematoplexus branch knot

As usual with Nematoplexus, the internal structure of the knot is not revealed even with higher magnification. The tubes of 3Ám diameter sticking out on the left do not justify the assumption that there are lots of them inside. One recurved tube seen on the left seems to indicate that these tubes tend to keep near the knot.
What seems to be another type of tubes, diameter 2Ám or less, extend right away from the knot. One is faintly seen in Fig.2 turning towards the right edge, and another one, hardly seen, towards the upper edge of the image.
Sample: Rh14/35 (0.17kg), Part 1, found in 2015.

Considering that Nematoplexus has turned out to be more complex than previously assumed [1], further investigations with adequate magnification are expected to provide information which should help to find a place for this enigmatic organism on the Tree of Life.

H.-J. Weiss     2018

[1]  A.G. Lyon: On the fragmentary remains of an organism referable to the nematophytales, Nematoplexus rhyniensis.
      Trans. Roy. Soc. Edinburgh 65(1961-62), 79-87, 2 plates.        (Scale error on Plate I Fig.1: not x19 but x1.5)
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