Ophioglossoid ferns

Order Ophioglossales

The Ophioglossoid ferns are a cryptic group of small fern-like plants called the Rattlesnake ferns, Grape ferns, Moonworts, and the Adder's-tongue ferns. All members are composed of a single upright vegetative leaf and a single fertile leaf. Some have a small compound frond, and others have an entire leaf. One taxon, Ophioglossum reticulatum, has the highest chromosome number of any known organism (2n=1260)! In a phylogenetic analysis, the Ophioglossales form a sister group with the whisk ferns (i.e. Psilotum & Tmesipteris).

Above: (left) Ophioglossum; (center-left) Botrypus; (center-right) Botrychium; (right) Helminthostachys

Ecology and habit

  • Temperate and tropical terrestrial and epiphytic plants

Sporophyte (=spore-bearing phase)

Vegetative features

Stem

  • Corm-like rhizome

  • Siphonostelic vascular architecture

  • Periderm production has been reported in Botrychium, Botrypus, Helminthostachys, and Ophioglossum ( Peterson 1971, Takashi and Kato 1988).

  • Some reports indicate secondary xylem (wood) in this group, but close examination of Botrychium indicates there is no vascular cambium, nor is there secondary phloem (Rothwell & Karrfalt 2008)

Leaves

  • Compound or simple leaves; megaphylls

  • Single vegetative leaf

  • Single fertile leaf

Roots

  • Roots present

Reproductive features

Sporangia

  • Sporangia, born in clusters on fertile leaf (sporophyll)

  • Sporangia are eusporangiate (larger sporangia with many spores)


Gametophyte (=gamete-bearing phase)

  • Gametophytes are subterranean, lacking chlorophyll

  • Symbiosis with an endophytic fungus provides the requisite nourishment

Diversity

Family Ophioglossaceae

  • Ophioglossum

  • Ophioderma

  • Helminthostachys

  • Mankyua

Family Botrychiaceae

  • Botrypus (the rattlesnake fern)

  • Sceptridium (the grape-ferns)

  • Botrychium (Moonworts)

Classification

└Embryophytes

└Tracheophytes

└Euphyllophytes

└"Ferns" (sensu lato)

└Ophioglossales

Geologic Age

  • ??? - present

Above: Fertile and vegetative leaves of Ophioglossum

Above: Compound leaf of Botrychium

Above: Fertile and vegetative leaves of Botrychium lunaria

Additional Resources