Glades in the nematophyte jungle
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Nematophytes are still enigmatic as a whole and in detail as well. Usually they involve random but
rather even distributions of filamentous tubes occasionally interspersed with so-called branch knots consisting of a dense tangle of tubes and supposed to be somehow related to tube formation [1]. Examples of such knots, with tubes connected to them, are seen in Rhynie Chert News 13, 51, 71. Clots of a different aspect but also found between nematophyte tubes deserve closer inspection. After a first inspection they had been taken for branch knots in Rhynie Chert News 38, 40 but this must be reconsidered now. The tubes are seen avoiding the "glades", with only a few exceptions. There seem to be no tubes obviously starting from there as they do from branch knots of other nematophytes. Also there seems to be no inner structure in the glades. The tiny bright dots seen somewhere are probably glittering crystals, not sections of tiny tubes.
nematophyte with clotnematophyte with clotnematophyte with clotnematophyte with clot
nematophyte with clotnematophyte with clotnematophyte with clot
Figs. 1-7: Nematophyte consisting of rather well aligned tubes, mainly 50-60Ám across, randomly distributed but apparently avoiding several rounded "glades" of 0.35-0.5mm seen on the cut face with a frequency of about 10/cm2.
Fig.3: Partially decayed area.

The size of every image is 1mm2.









Unfortunately, there is no good lengthwise cut of this nematophyte available at present so that one cannot be sure whether or not some tubes somehow start from the periphery of the glades. The latter phenomenon is suggested by a few short tube parts with deviating directions in Fig.2. It is not known why Fig.6 seems to indicate the contrary: no tube touching the periphery.

Fig.8: Nematophyte tubes, slightly deranged and separated, thus individually visible in lateral view.
nematophyte tubes
         The tiny white dots are due to the roughness of the raw sample surface. Same scale as above.

Judging from small fracture faces along the
densely spaced tubes which offer a sideways view, even a polished longitudinal section would only offer a confusing assembly of lines with poor contrast which would not look like tubes. Individual tubes can be seen in lateral view if they are displaced and separated by white chalzedony as in Fig.8.
The stronger contrast in Figs. 1-7 compared to Fig.8 does not indicate better preservation or
thick-walled stiff tubes but is simply an optical effect. The thick black wall often seen on cross-sections may be due to some microbial layer which is inconspicuous in lateral view. Other microbial sheets are seen as black lines connecting the tube sections, as in Fig.6.
The small-scale waviness seen in Fig.8 seems to indicate that the tubes had been rather soft before silicification, which had also been deduced from observations in Rhynie Chert News 40.

Finally we are left with the question what to think of the smooth glades among the tubes which look so much different from the nematophyte branch knots as we know them.

H.-J. Weiss      
2016


[1]  www.abdn.ac.uk/rhynie
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