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Psilophyta-Tmesipteris-1 |
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Tmesipteris
is a small genus with only 2-3 species. 
Unlike Psilotum it has a
restricted distribution & is only found in Australia, New Caledonia & New Zealand.
Like Psilotum, it is a Pendulous Epiphyte which can also be found on the ground.
Tmesipteris has Rhizomes which becomes upright Stems, like (you guessed it) Psilotum.
However, its Aerial Stem looks like a Fern Leaf!
The lower part of the Aerial Stem has small scale-like projections. These become larger towards the apex.
The flat projections from the upper part of the Aerial Stem will be called "Leaves".
Synangia composed of 2 Sporangia are found at
the base of
larger leaves. Anatomically they are very similar to Psilotum.
The larger Leaves are much Longer and Broader than those of Psilotum.
Furthermore, the largest Leaves contain a single Vascular Bundle which connects it to the central stele. These could be called Microphylls.
There is no Petiole and the leaf base is broadly attached to the Stem.
The Leaves of Tmesipteris are ambiguous & are considered to be part of the Stem by most botanists.
This is supported by the observation that Rhizome stems are converted into Aerial Stems in a seamless manner. This means that a Rhizome Apex becomes the Apex of an Aerial Stem without lateral branching.
If the Aerial Stems had a Lateral origin, Tmesipteris would closely resemble a Fern.
The Stele in the Aerial Stem is more complex than in Psilotum & approaches what we see in later Divisions.
One trend to keep in mind is that the complexity of the Stele is related to the complexity of the Leaves.
The combined traits seen in the Psilophyta suggest that they are related to the Eusporangiate Ferns. We will encounter these later in the course.
The Synangia are associated with two
leaves.
This is similar to Psilotum. The Sporangia split longitudinally when they are mature.
Their spores and Gametophytes are very similar to Psilotum.
