Pseudo-cells in Rhynie chert
cherts with or without silicified higher plants may show confusing
structures resembling plant tissue while being no such. In Fig.1, the
"cells" seen in the odd-shaped areas of decayed and vanished tissue in
rhizome do not seem to differ much from the
cells of the latter, at least with
respect to shape and size distribution. The conspicuous horizontal
boundary above the structure indicates the former presence of a watery
Fig.1 (right): Nothia rhizome
cross-section with central strand, surrounding tissue decayed and
replaced by coated fungus hyphae and pseudo-cellular structure grown in
formerly water-filled places.
Fig.2 (left): Formerly water-filled cavity with
thick lining of silica gel, grains of irregular shape grown inside.
What seems to be mutually contradictory, a
horizontal boundary above some structure in Fig.1 but
below in Fig.2, may be surprising. In Fig.2, a pale brown watery
suspension had settled at the bottom of the
water-filled cavity, making
a horizontal surface, and eventually solidified into gel.
Then the remaining cavity got a
thin white lining all around, clearly seen only at the bottom where
it appears in
cross-section. Then came a thick pale white lining, appearing
unevenly thick owing to varying orientation with respect to the cut
plane. The granular structure within does not look as much like tissue
as the structure in Fig.1 does. It seems that the horizontal boundary
of the latter, as well as a similar boundary in Fig.3, had been brought
about by some watery suspension settling in the lower part of the
cavity but there is no obvious reason why the structuring had been
restricted to that area.
Fig.3 (below): Pseudo-cellular structures grown
formerly water-filled cavities between silica gel.
Width of the picture 4.3mm.
Figs.4,5: (below right): Details of Fig.3
Fig.6 (right): Detail of Fig.3, possibly leading the way to
a partial explanation of the phenomenon of pseudocells.
pseudo-cellular structure is seen in Fig.6 above and below. Apparently
it has originated from whitish clots abundantly seen in the
middle of the cavity. The growing globular clots would not fuse when
touching but keep their individuality and mutually squeeze into a
pattern resembling plant tissue. The illusion is favoured by
fact that the pseudo-cells are separated by dark boundaries which
possibly consist of microbes living on the surface of the clots or
pushed ahead by the expanding surface and getting trapped.
could even be the primary cause of the phenomenon. This is suggested by
the observation that the pseudo-tissue is often much darker than its
surroundings. On the left of Fig.5 there is a dark fill of
a narrow former cavity between whitish silica gel (all chalzedony now),
with only one small globular clot, apparently retarded in growth
compared to the bigger clots on the right of Fig.5. Hence, one can
assume that first came the dark, then the clots.
Dark deposits, layers, and crusts occasionally seen in Rhynie chert are
most probably due to microbial activity (See Rhynie Chert News 87 .)
is not known how the microbes, which are not often present in
water-filled cavities left during silicification, can trigger the
formation of globular clots with sizes incidentally like those of plant
cells, thus making pseudo-tissue. Judging from the available samples,
they would not trigger the formation
of clots of much deviating sizes.