Psilotum nudum

Alexis continues with the prehistoric plant series she assembled in the summer:

Thank you to Forest & Kim Starr for sharing their photos from Maui, Hawaii via Wikimedia Commons (photo 1 | photo 2). Psilotum nudum grows in subtropical and tropical conditions and can be epiphytic.

Plants of the Psilotales, such as the pictured Psilotum nudum, are recognized as the most primitive plants currently living. Psilotum species are known as whisk ferns and though they do not appear in the fossil record, they share characteristics with extinct flora like Cooksonia.

The Rhynie Chert in Scotland is a sedimentary rock formation that contains a variety of fossilized plants and animals from the Early Devonian period, about 400-412 million years ago. It contains very well-preserved specimens of early vascular plants like Aglaophyton, which, like today’s Psilotum, had no true leaves or roots, possessed rhizomes and sporangia, and a dichotomous branching pattern. Additionally, there is evidence that Aglaophyton species were myco-heterotrophic, having a symbiotic relationship with arbuscular mycorrhizal fungi that helped the plant to absorb nutrients; fungi often associate with present-day members of the Psilotales in the same way. Because of their similarities to Devonian flora, whisk ferns are uniquely significant for research purposes.

Psilotum nudum
Psilotum nudum

7 responses to “Psilotum nudum”

  1. Larry Ayers

    Fascinating photo and description! I was unaware of the genus until now. I’m forwarding the link to a friend. Thanks!

  2. Santiago Ramírez

    Nice pictures.
    The description you make fits perfectly to the Rhyniopsida, a group of extinct plants that includes Cooksonia and Rhynia. However similar Psilotum is to these primitive plants, it has no close relationship (phylogenetic) with them. The simplified architecture is not a shared characteristic, but represents a convergence of form.
    In fact, Psilotum and sister genera Tmesipteris are part of the order Psilotales, which is a group of ferns related to common ferns, tree ferns and horsetails. Actually, the most basal vascular plants are the Lycopods, which Psilotum lags in about 100 million years.
    If you are interested you should read Pryer et al. (2004). American Journal of Botany 91.

  3. Sue Vargas

    Weird and wonderful! Thanks

  4. Brian

    great series of photos – thank you!
    i have a couple of comments:
    1. The plants shown are quite short probably reflecting poor growth conditions. Psilotum nudum can get up to 50 or 60 cm. Larger plants are usually drooping or arching.
    2. I really do not think that “Plants of the Psilotales, such as the pictured Psilotum nudum, are recognized as the most primitive plants currently living” is accepted anymore(2011). On molecular evidence they reside firmly within the monilophytes (ferns etc). Perhaps a better statement would be “Plants of the Psilotales show the simplest structure of any living vascular plant”
    boa sorte and thank you

  5. Michael G. Simpson

    Yes, I agree with Brian. Psilotum and relatives has been shown to be nested well within the monilophytes (“ferns,” in the broad sense) and only superficially resembles early vascular plants, a concept promoted by Bierhorst decades ago. And, it is not really best to call any plant lineage “primitive,” as that (or the alternative “ancestral”) should best be reserved for characters, not lineages.
    Very nice photos. I recall seeing Psilotum in Kaui years ago.

  6. Lisa Haglund

    I absolutely love this series. Seeing images of and learning about prehistoric plants and how they have evolved over time has been facinating. I hope you will do another series like this in the future. Thank you!

  7. Elizabeth Revell

    Also, P. nudum is not totally restricted to the tropical/sub-tropical zones, as it is a plant found in New Zealand, as far south as Lake Taupo – although admittedly usually in soils warmed by thermal activity … but that’s still all relative, as Lake Taupo and its environs can get pretty darn cold in winter. Yes, I know, not anything like the north of North America, but still cold.
    I’ve certainly seen it flourishing trackside in the Waiotapu valley area outside the seriously warmed thermal parts of the valley.

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