Tubes at Nematoplexus
its discovery , new finds of this "enigmatic organism"  known
from the Rhynie chert only have
provided new problems in addition to a few answers to old
questions. Apparently it is either unbelievably
versatile as a species or it is nearly always associated with one
or more other
nematophyte species. Anyway, Nematoplexus
is very peculiar, as indicated by this picture.
spiralling ones (10-12Ám) near two obscure "knots" on the right, a
bunch of straight ones below the middle, a long bow dimly
seen in the
depth, and broader slightly curved ones (18Ám) above. Image width 2mm.
The various aspects of Nematoplexus tubes
evident from own chert finds have been described in previous
contributions, as in Rhynie
Chert News 29,
The present contribution is meant to draw
attention to the so-called
branch knots. Usually they are surrounded by a tangle of tubes so the
very "knot" is not seen. Since the conspicuous
tubes are never seen branching, the
simple idea came up that there might be profuse branching
the knots. This seemed to be compatible with the questionable statement
in , p.80, that "tubes can be seen entering and leaving them." Hence
term "branch knot" was
accepted as if it were an explanation of how the tubes are
There are two "branch
knots" in Fig.1, which is a rare coincidence but is not relevant here.
The upper one is divided by the big straight crack, which has provided
the rare opportunity to
illuminate half the knot
with reflected light such that a rare sight has become visible in
Fig.2: A kind of
foot of a spiralling tube below left is seen connected to a kind of
surface of the central
body of the "branch
spiralling tube apparently
begins on the dark side
of the divide with a
broad foot, too.
"knot", detail of Fig.1 above right: other orientation, magnification,
width 0.2mm. Photograph by G. Schmahl.
Even though Fig.2 may seem rather confusing, it
some information: The
usually hidden central part of the "branch
knot" is not simply a dense tangle of spiralling tubes. It is a
separate clot with a rugged surface of granular appearance, where the
spiralling tubes (11Ám) start from, without any branching. If there is
some kind of branching unseen inside, it does not produce the
"knot" with 4Ám-tubes and
only one stump of the spiralling 12Ám-tubes left.
Image width 0.11mm. Photograph
by G. Schmahl.
globular shape of the central clot may become clearly visible when the
spiralling tubes decay and
vanish, as with the clot in Fig.3, seen amidst
decaying 12Ám-tubes in
Chert News 133.
This clot seems to be similar to the one in Fig.2: no
smooth surface, here with short (?) 4Ám-tubes poking out. Less
conspicuous than in Fig.3, a few 4Ám-tubes are also seen in Fig.2. Probably
the 4Ám-tubes have mostly
been overlooked but on
some clots they are absent: Rhynie
Chert News 136.
The considerable diversity of Nematoplexus as
indicated by Fig.1 is even topped by the big variant described
Chert News 135,
here Fig.4. It is a
clot with a fuzzy surface
where the big tubes seem to stick with a club-like broadened "foot".
big tubes are of the same type as the 18Ám-tubes in
Fig.1. The picture plane apparently cuts through the clot near the
surface, revealing circular sections of some tube "feet", up to 34Ám,
but no big tubes branching.
few thin tubes, 4-5Ám, are seen
emerging from the clot. Higher magnification reveals an irregular
the clot but no branching
tubes, as seen in Rhynie
Chert News 135,
"knot" with slightly
of 17-22Ám and 4-5Ám,
separate 8Ám-tube of unknown affiliation; crack stained with
width 1.3mm, same scale as Fig.1.
appears that the statement in  that "Branching
of the tubes occurs in
...very tightly coiled knots of tubes showing repeated and closely
spaced branching" does not apply to the conspicuous
tubes seen here, spiralling or not. They
do not branch, neither inside nor elsewhere. Some
of the clots are so small that there would not be enough room for "tightly
branching" tubes: Rhynie
Chert News 136,
The idea of "tubes ...
entering and leaving" the knots  is misleading. Apparently the tubes
come from the surface or
near the surface of the
clot, where they possibly are in contact with an internal structure possibly
involving very thin tubes
of a different type . However, no
tubular structures have been seen inside the
above clots, not even with higher
magnification in the clot of Fig.4.
question concerning the origin of the tubes has been partially answered
here but other questions have remained unanswered: Why do the tubes of Nematoplexus vary
tremendously even in one chert sample:
straight, curved, and spiralling ones with several diameters,
smooth-walled and patterned ones ?
Sample: Rh14/35: Fig.3;
 A.G. Lyon:
On the fragmentary remains of an organism referable to the
nematophytales, from the Rhynie chert, Nematoplexus rhyniensis.
Trans. Roy. Soc. Edinburgh
65(1961-62), 79-87, 2 tables.
 T.N. Taylor,
E.L.Taylor, M. Krings: Paleobotany, Elsevier 2009.