Gnetophyta

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The plant division Gnetophyta or gnetophytes comprise three related families of woody plants grouped in the gymnosperms, a paraphyletic group of seed plant divisions. The gnetophytes differ from other gymnosperms in having wood vessels as in the flowering plants (Angiosperms or Magnoliophytes), and it is thought that Gnetophytes may be the group of spermatophytes most closely related to the flowering plants.

Gnetophyta contains only one class of living plants, class Gnetopsida. The class is divided into three orders, each containing a single family and genus:

Gnetales: Gnetaceae; Gnetum
Welwitschiales: Welwitschiaceae; Welwitschia
Ephedrales: Ephedraceae; Ephedra

The Gnetales consist of a single genus, Gnetum, which are mostly woody climbers in tropical forests. However, the most well-known member of this group, Gnetum gnemon, is a tree. The seeds produced are used to produce a crispy snack known as 'Keropok Belinjau' in Malaysia and Indonesia. The Malay name for this plant is 'belinjau'.

The Welwitschiales comprise only one species, Welwitschia mirabilis. It grows only in the deserts of Namibia. The plant is strange in having only two large strap-like leaves for all its life. These grow continuously from the base, and are usually tattered at the ends by flapping in the winds.

The Ephedrales consist of a single genus Ephedra, and are known as the jointfirs because they have long slender branches which bear tiny scale-like leaves at their nodes. Ephedra is reputed to have medicinal properties, but has recently been banned by the FDA due to harmful and potentially deadly side effects.

References

Bowe, L. Michelle, Gwénaële Coat, and Claude W. dePamphilis. 2000. Phylogeny of seed plants based on all three genomic compartments: Extant gymnosperms are monophyletic and Gnetales' closest relatives are conifers. Proceedings of the National Academy of Sciences 97: 4092-4097.
Soltis, Douglas E., Pamela S. Soltis and Michael J. Zanis. 2002. Phylogeny of seed plants based on evidence from eight genes. American Journal of Botany 89: 1670-1681 (abstract [here]).
Chaw, Shu-Miaw, Christopher L. Parkinson, Yuchang Cheng, Thomas M. Vincent, and Jeffrey D. Palmer. 2000. Seed plant phylogeny inferred from all three plant genomes: Monophyly of extant gymnosperms and origin of Gnetales from conifers. Proceedings of the National Academy of Sciences 97: 4086-4091 (abstract [here]).

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