Re-interpretation of detail on Aglaophyton
gametophyte
The
gametophyte of Aglaophyton
(formerly known as Rhynia
major) had
been discovered in the Lower Devonian Rhynie chert by
Remy & Remy
and named Lyonophyton
rhyniensis
[1]. In later papers by Remy
& Hass
it had been thoroughly described [2,3]. However, a photograph of a
detail
in [3] strongly suggests an interpretation differing from the one
offered
there (Fig.1).
Fig.1: Epidermis of Lyonophyton,
arrows
(supposedly) indicating “secondary divisions” of cells in the vicinity
of a stoma,
after [3,4].
It is described there as “Epidermis
of young gametophyte aerial axis showing secondary divisions of
subsidiary cells (arrow heads) that will lead to the formation of
rhizoidal bulges”. Conclusions are drawn there from this picture: “Such
axes represent adaptations to subaerial and aerial conditions. In the
basal portion of slightly older axes, the subsidiary cells of each
stomatal complex show secondary serial divisions that develop into
rhizoids. This suggests a functional change in the basal parts of the
axes from aerial to rhizomatous.”
The alleged secondary divisions are really
shrinkage cracks,
which
becomes obvious in Fig.2, where the cell walls and the
questionable thin lines faintly seen in Fig.1 have been redrawn for
better visibility.
Fig. 2: Drawing after Fig.1, revealing the true
nature of the faint lines as shrinkage cracks in chalcedony.
Hence, the above conclusions derived from this figure in [3] are not
substantiated. The same figure and its misinterpretation have been
published once more [4].
H.-J. Weiss
2005, emended 2014
[1] W.
Remy, R. Remy : Lyonophyton
rhyniensis
…,
Argumenta Palaeobotanica (Münster)
6(1980), 37-72, Tafel 7-13.
[2] W.
Remy, H. Hass : Ergänzende Beobachtungen an Lyonophyton
rhyniensis,
Argumenta Palaeobotanica (Münster)
8(1991), 1-27, Tafel 1-12.
[3] W.
Remy, H. Hass : New information on gametophytes
and
sporophytes of Aglaophyton
major and inferences ...
Rev. Palaeobot. Palynol. 90(1996),
175-193.
[4] D.
Edwards, H. Kerp, H. Hass: Stomata in early land
plants,
J. Exp. Botany 49(1998) Special Issue,
255-278.
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