Rhynie Chert Flora:
Basic Information on the Remaining Plant
Groups in the Rhynie Chert
A number of other flora have been described from the Rhynie chert, including
the enigmatic nematophytes, cyanobacteria, various types of algae (including
simple filamentous and unicellular chlorophytes, and stoneworts or
Various types of fungi are also present, including terrestrial and aquatic
types; the earliest recorded lichen has also been described.
An extinct, enigmatic group of plants comprising primarily an inner loose
mesh-like plexus of spirally coiled tubes. The tubes may be smooth-walled
or show spiral-thickenings; branching of these takes place in small knots.
The tubes become closely packed, and may be orientated perpendicular towards the edge of the plexus where they
meet an outer cuticular envelope.
Two nematophytes are known from the Rhynie chert: Nematophyton
taiti (Kidston & Lang 1921b)
(see inset right) and Nematoplexus rhyniensis (Lyon
1962). Both are generally fragmentary and poorly preserved.
The gross morphology of nematophytes is not fully known, though some
Carboniferous types are believed to have resembled prostrate logs, perhaps
with fronds. Their internal structure show similarities with certain
algae, and the spirally thickened tubes resemble the tracheids
in vascular plants.
The habitat of nematophytes is also not fully known, but they may have
been semi-aquatic plants with emergent fronds.
Above: Nematophyton taiti, showing loose plexus
of coiled tubes (centre and bottom) with branch knots (b), passing
upward into more tightly packed orientated tubes (top) with a probable
external cuticle layer (c) (scale bar = 1mm).
These are simple photosynthetic bacteria, commonly termed cyanobacteria.
These may be unicellular organisms or comprise filamentous chains of
cells. Being prokaryotic organisms, the cells do not contain nuclei.
A number of probable cyanobacteria are found in the Rhynie chert, some contributing to distinct stromatolitic laminae
in the laminated cherts, possibly having originally grown as
cyanobacterial mats on sinter surfaces. Other types are found within
'clotted' chert textures, being deposited in more aquatic settings, and
still others within decaying plants (see inset right).
Some of the Rhynie cyanobacteria, such as Archaeothrix (inset
right), possessed heterocysts and therefore probably played a
significant roll in fixing atmospheric nitrogen into the soil.
Above: Filaments of the cyanobacterium Archaeothrix
oscillatoriformi within a stem of Rhynia gwynne-vaughanii (scale bar =
Chlorophytes or green algae are photosynthetic eukaryotic organisms.
Being eukaryotes their cells contain nuclei. They may be unicellular or
form filamentous chains of cells, or may form more complex structures such
as stoneworts or charophytes (see below). Most are found in freshwater
A number of filamentous and unicellular chlorophytes are known from the
Rhynie chert, particularly in chert beds deposited in aquatic
environments, though very often the poor preservation of cell contents
makes their identification very difficult (see inset right).
Above: A number of unicells in Rhynie chert. Some of these displaying cell contents may represent unicellular eukaryotic algae (scale bar =
Charophytes are large structurally complex green algae. These plants
comprise a series of multi-cellular nodes and long single cells or internodes.
Branching occurs at the nodal cells and may be repeated. Charophytes also
exhibit structurally complex gametangia. These organisms are
aquatic, living in fresh to brackish water.
One probable charophyte has been described from the Rhynie chert, Palaeonitella
cranii (Kidston & Lang
1921b). The reproductive structures of Palaeonitella have not
been discovered and therefore its status has not been fully resolved.
Palaeonitella was an aquatic plant, being commonly found within
'clotted' chert textures, along with the crustacean Lepidocaris.
Right: Palaeonitella cranii showing clusters of
nodal cells (n) interspersed with long internodal cells (p).
Lateral branches (l) are emerging from the nodes (scale bar =
Fungi are multi-cellular, non-photosynthetic eukaryotic organisms,
generally being saprophytic (feeding on dead organic matter) or parasitic
in their lifestyle; though some types form symbioses with plants (endotrophic
mycorrhizae), or with an alga or cyanobacterium to form lichens.
Numerous fungi are recorded from the Rhynie chert (Taylor
et al. in press), including the
earliest best preserved examples of endotrophic mycorrhizae in plant
(Taylor et al. 1995b) (see
inset right). The earliest ascomycetes (true fungi that produce their spores
within a sack-like structure called the ascus) are also present (Taylor
et al. 1999, in press); together with various tiny aquatic or soil
or chytrids. A number of the latter have shown evidence of parasitism on
other Rhynie plants and even on other fungi (an interaction called mycoparasitism).
Above: Endotrophic mycorrhizae (f) occupying
intercellular spaces within the cortex of Aglaophyton major (scale
bar = 30µm) (Copyright owned by University
Lichens are non-vascular plants formed by the symbiotic relationship
between a fungus and an alga or a cyanobacterium. The
lichen thallus comprises distinct layers of fungal hyphae (the mycobiont)
and the alga/cyanobacterium (the photobiont).
The earliest lichen is recorded from the Rhynie chert, Winfrenatia
et al. 1995, 1997) (see inset
right). Winfrenatia most likely colonised hard substrates. Degrading sinter surfaces
could have provided a suitable substrate. It may have been able to weather the rock
surfaces it was colonising, thus contributing to soil formation.
Above: Longitudinal view of the thallus of Winfrenatia reticulata.
Tightly aggregated fungal hyphae (F) can be seen (the
mycobiont). The surface of the thallus showing a series of pockets (P)
with nets of fine hyphae containing the cyanobacterium (the photobiont) (Copyright owned by University Münster).