Pteridophytes
Spore-bearing, vascular plants
The pterdiophytes, or fern allies, are vascular plants bearing spores during reproduction, and exhibit a diplo-haplontic lifecycle (alternation of generations) with a dominant sporophyte stage. It is a group of plants that share similarities in life cycle, ecology, and physiology, and are considered a polyphyletic grouping. The name pteridophyte means "feather-plant", denoting the feather-like leaves of ferns. Not all members of this group have large, feather-like leaves, and some even lack leaves and roots all together.
Above: (far left) clubmosses; (middle left) whisk fern, Psilotum; (middle right) Horsetail, Equisetum; (far right) Christmas fern, Polystichum
Plants called pteridophytes combine two clades: the Clubmosses (aka Lycophytes) and the Ferns / Horsetails (aka Monilophytes).
The Clubmosses (Lycopodiophyta) are herbaceous spore-bearing vascular plants with small leaves called microphylls. They were an extremely successful group 100s of millions of years ago (e.g., Devonian and Carboniferous) and are represented by the living ground pines, spike-mosses, and quillworts today.
The Ferns (Polypodiophyta) are herbaceous spore-bearing vascular plants with true leaves called megaphylls. They represent the 2nd-most successful extant spore-bearing vascular group represented by the true ferns, ophioglossoid ferns, and marattioid ferns. The horsetails and whisk ferns (psilophytes) are also spore-bearing, but with absent or non-functional leaves. They do not look fern-like, but appear to be evolutionarily related to ferns
Diversity, extant
Clubmosses / Lycophytes (Lycopodiophyta)
Ground pines (Lycopodiales)
Quillworts (Isoetales)
Spike-mosses (Selaginellales)
Monilophytes (Polypodiopsida)
Horsetails (Equisetophyta)
Ophioglossidae
Ophioglossoid ferns (Ophioglossales)
Whisk ferns (Psilotales)
Marattioid ferns (Marattiidae)
True ferns (Polypodiidae)
Classification
Archaeplastida (Plants)
└Viridiplantae (Green plants)
└Embryophytes
└Tracheophytes (vascular plants)
├Clubmosses (Lycophytes)
└Euphyllophytes (true-leaved plants)
Geologic Age
Silurian - present
Sporophyte (=spore-bearing phase)
Vegetative features
This phase is dominant, multicellular and photosynthetic
Stems / leaves
Possess vascular tissue (xylem & phloem)
Many have complex anatomy patterns of primary xylem and phloem
Secondary xylem mostly absent in living forms (except Isoetes), but found in the extinct clubmosses (Lepidodendrales), fossil horsetails, the cladoxylopsid and rhacophyte ferns,
Most possess leaves: either microphylls (clubmosses) or megaphylls (all other vascular plants)
Psilophytes do not appear to possess leaves, either by loss or ancestry
Reproductive features ferns
Produce sporangia on either leaves (=sporophyll) or short stems (=sporangiophore)
Mostly homosporous (=spores all the same size/shape)
Several derived groups are heterosporous (i.e. 2 different types of spores: megaspores, microspores)
Heterosporous forms found in Selaginella, Isoetes, and the water ferns (Marsilea, Azolla, etc.)
Gametophyte (=gamete-bearing) phase
Smaller than sporophyte, but independent and multicellular
Many are also photosynthetic (thalloid)
Produce sperm-bearing structures (=antheridia)
Produce egg-producing structures (=archegonia)
Questions for Thought
What is a "pteridophyte" and why is this a useful educational term?
How is the life cycle of a fern different from a moss?
What does the gametophyte of a fern look like?
What does the sporophyte of a horsetail (Equisetum) look like?
What aspects of Psilotum's morphology are considered ancestral?
What is a synapomorphy for the clubmosses?
What are the differences between ground pines, spike-mosses, and quillworts