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Aglaophyton †

Paravascular, branching plants

Aglaophyton † is an extinct, spore-bearing, non-vascular plant that was small, leafless, and rootless, but produced forked upright stems with terminal spore cases. It has a well-known sporophyte phase from the Rhynie chert and has been shown to have a gametophyte phase called Lyonophyton †. This plant lacked true vascular tissue but had simple water-conducting cells like mosses. Today, all living non-vascular plants lack the ability to branch in the spore-bearing phase, and Aglaophyton represents an intermediate stage of plant evolution.

Ecology & Form

Sporophyte (Spore-bearing phase)

Aglaophyton majus †

Stem

Isotomous aerial axes/stems and rhizomes
15 cm in height, and a maximum width of 6 mm
No true vascular tissue
- Distinct, hydroid-like conducting cells (Edwards, 1986)
Stomata found on aerial and rhizomatous axes (Edwards et al., 1998)
- The presence of stomata and preservation in the Rhynie chert suggests that these rhizomes crept on top of the soil.
- It is assumed that these stomata had passive control, in which the loss of turgor pressure from drought resulted in stomatal closure

Rhizome

Evidence of mycorrhizal fungi found associated with the rhizomes
- Glomites rhyniensis †, a fungus attributed to the glomeromycetes, formed arbuscules in the aerial axes and rhizomes to exchange nutrients with the plant (Remy et al., 1994; Strullu-Derrien et al., 2014)
- Rugososporomyces lavoisierae †, another fungus attributed to the glomeromycetes, formed arbuscules in the aerial axes (Strullu-Derrien et al., 2025)

Leaves

No leaves; aerial axes are leafless
It is assumed that the aerial axes were green & photosynthetic

Roots

Rootless, but it exhibited rhizoids

Geologic Age

Mid-Silurian (?) - Early Devonian

Classification

└Embryophytes

└Polysporangiophytes

└Aglaophytes †

Reproduction

Spore-bearing, homosporous plants
Sporangia are relatively large, fusiform in shape, with spiral slits for dehiscence of spores
- Aerial axes are terminated by these sporangia
No columella is present in the sporangium
- Columella is present in other non-vascular plants such as mosses, hornworts, and Horneophyton †
Stomata are found on sporangia, but at a lower frequency than on axes
- Stomata in these ancestral plants may have promoted dehiscence of sporangia (Chater et al., 2016)

Above: lifecycle of Aglaophyton-Lyonophyton †

Gametophyte (gamete-forming phase)

Lyonophyton rhyniensis †

Remy & Remy, 1980
Form genus of the male gametophyte; female gametophytes have been discovered but never described
Aerial axis that widens and terminates in a conspicuous cup-like structure, which bears the antheridia
Smaller than a sporophyte, but the axis of the gametophyte is very similar in anatomy
Possibly independent from the sporophyte, but may be connected and reliant on the female gametophyte for nutrition
This gametophyte phase possesses stomata, which is unique among land plants
- No bryophytes possess stomata in their gametophyte stage, only in the sporophyte on the sporangium.
- Hornworts possess a 2-cell pore complex similar to stomata, but these pores lack the complexity of sporophytic stomata

Above: Thin section of a Lyonophyton † male gametophyte (with an antheridium) from the Rhynie chert.

Left: Reconstructions of the female (left) and male (right) morphologies of Lyonophyton †

Above: Model of an early land plant, Aglaophyton, employing apical growth to grow aerial axes. In this hypothesis, axes are created as apical meristems grow upwards, leaving cells to expand and mature. This mode of growth is seen in the Lycopodiaceae.

Above: Model of an early land plant, Aglaophyton, employing intercalary growth to grow aerial axes. In this hypothesis, several orders of axes are pre-formed before lengthening and then expand through intercalary growth between the branching points. This form of growth is seen in Psilotum and Equisetum.

Diversity

Few species, with Aglaophyton as the main representative

Aglaophyton majus †

Early Devonian (Lochkovian–Pragian) from Rhynie Chert in Aberdeen, Scotland
See descriptions above
Originally named Rhynia major, but was separated from that genus since this plant does not have vascular tissue

Teruelia diezii †

Cascales-Manana & Gerrienne, 2017
Early Devonian (Lochkovian–Pragian) from the Nogueras Formation of the Iberian Peninsula
Compression fossil with isotomous branching
Robust stems terminated in large, fusiform, twisted sporangia
This taxon is probably the compression fossil representative of Aglaophyton, which is known only from permineralizations

Above: Reconstruction of Teruelia diezii † (from Fig. 4, Cascales-Manana & Gerrienne, 2017)

Additional Resources

The Rhynie Chert and its Flora

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