- Where the spirals come from
The enigmatic "branch knots", scattered among the
of the enigmatic organism
Nematoplexus seldom found in the famous Rhynie chert ,
been thought to be places where the tubes branch profusely although a
branching tube has apparently never been seen.
Fig.1: Spiralling tubes of Nematoplexus
two related "knots".
As seen in Fig.1 (reproduced from Rhynie
Chert News 71
the tangle of randomly distributed
tubes with dark "knots" in between is confusing, all the more so since
straight or weakly curved tubes may also be present: Rhynie
Chert News 51,
A region near the black spot on the right has
been photographed anew with higher magnification and other
illumination: Fig.2. (Note
that Fig.2 is turned with respect to Fig.1.) What is seen here
can tentatively be interpreted as follows: A small protruding
part of the big black
knot in the depth of Fig.1 on the right is seen on the left of Fig.2.
By lucky coincidence,
a small separate knot, not noticed in Fig.1 but now in the middle of
Fig.2, is divided
by a tilted crack plane
reflecting the incident light so that half
the knot, left of the divide, is illuminated from below while the other
half, right of the divide, keeps
in the shade. (The
off-white angular mineral body can serve as a mark for
comparison with Fig.1. The
bright white spot below is an irrelevant light reflex
from applied oil.) The colourful illumination of the tubes is due to a
thin deposit of iron oxide on the reflecting crack face.
Fig.2: Small "knot" incidentally divided by a crack in the
chalzedony reflecting the incident light. Image
width 0.3mm. Photograph by Gerd
Most interesting is the junction of an
11Ám-tube to what seems to be the indefinite
surface of the knot: Contrary to the common belief due to
the established term "branch knot",
the tube is not produced by branching. The same
can be expected from the other tubes. One tube right of the divide, for
wider than normal where it emerges from the knot.
In addition to the tube diameters of 10-12.5Ám
in Fig.2, there is only one tube with 4Ám and a straight one with 17Ám.
(More non-spiralling tubes are present at other places in this sample.)
Sample: Rh15/79, Part 4, obtained from Barron in
Finally it can be stated that there is
evidence that the
spiralling tubes of
from the so-called branch knots
without any branching.
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