Class
Subclass
Order
Classification
Subordinate Taxa
Nomenclature
Scientific Name:
Psilotaceae J.W.Griff. & Henfr., Microgr. Dict. 540 (1855)
Type Taxon:
Description
Usually epiphytic or sometimes terrestrial ferns. Rhizomes long-creeping, dichotomously branched, subterranean, lacking roots. Aerial stems green, erect or pendulous, unbranched or dichotomously branched, angular to sulcate or flattened, glabrous, bearing rudimentary leaves. Leaves expanded and flattened or scale-like, spirally arranged or distichous. Vein single and undivided in each leaf, or absent. Sporangia thick-walled, sessile, fused to form bilocular or trilocular synangia, on the adaxial margin of forked sporophylls, lacking an annulus and dehiscing by a slit, maturing ± simultaneously, with 1000s of spores per sporangium. Homosporous; spores monolete, rugulate to smooth, lacking chlorophyll.
Taxonomy
A family of two genera and about 18 species (Chinnock 1998). The Psilotaceae includes terrestrial and epiphytic ferns with subterranean rhizomes that lack roots, pendulous or erect aerial stems that bear rudimentary leaves, have bi- or trilocular synangia on the adaxial margin of forked sporophylls, and a base chromosome number of 52.
The taxonomic placement of the family has had a controversial history. Traditionally the group was included within the fern allies, and often compared with early Devonian land plants, despite the fact that the Psilotaceae has almost no fossil record. Molecular evidence now clearly indicates that the family is an early-diverging group of ferns, and most closely related to the Ophioglossaceae (Pryer et al. 2001, 2004). Earlier, Bierhorst (1977) also suggested that the Psilotaceae was a primitive element within the true ferns, but he allied the group with Stromatopteris in the Gleicheniaceae, a view later discredited by Kaplan (1977) and Wagner (1977).
The family is represented in New Zealand by two indigenous genera, Psilotum and Tmesipteris.
Key
| 1 | Leaves tiny and scale-like, lacking veins; synangia trilobed | Psilotum |
| Leaves broad and flattened, with a single undivided vein; synangia bilobed | Tmesipteris |
Distribution
Psilotum is widely distributed in the tropics and subtropics, and Tmesipteris extends from tropical south-east Asia and the Pacific to temperate parts of Australia and New Zealand. Two non-endemic genera and six indigenous species present in New Zealand; two species endemic.
Biostatus
Indigenous (Non-endemic)
| Category | Number |
|---|---|
| Indigenous (Endemic) | 2 |
| Indigenous (Non-endemic) | 4 |
| Total | 6 |
Bibliography
Bierhorst, D.W. 1977: The systematic position of Psilotum and Tmesipteris. Brittonia 29: 3–13.
Brownsey, P.J.; Perrie, L.R. 2015: Psilotaceae. In: Breitwieser, I; Heenan, P.B.; Wilton, A.D. (ed.) Flora of New Zealand — Ferns and Lycophytes. Fascicle 9. Manaaki Whenua Press, Lincoln.
Chinnock, R.J. 1998: Psilotaceae. In: Flora of Australia. Vol. 48. 47–53.
Christenhusz, M.J.M.; Zhang, X.-C.; Schneider, H. 2011: A linear sequence of extant families and genera of lycophytes and ferns. Phytotaxa 19: 7–54.
Griffith, J.W.; Henfrey, A. 1855: The micrographic dictionary; a guide to the examination and investigation of the structure and nature of microscopic objects. Van Voorst, London.
Kaplan, D.R. 1977: Morphological status of the shoot systems of Psilotaceae. Brittonia 29: 30–53.
Kramer, K.U.; Green, P.S. 1990: Pteridophytes and gymnosperms. Kubitzki, K. (ed.) The Families and Genera of Vascular Plants. Vol. 1. Springer-Verlag, Berlin.
Mabberley, D.J. 2008: Mabberley's plant book, a portable dictionary of plants, their classification and uses. Edition 3. Cambridge University Press.
Pryer, K.M.; Schneider, H.; Smith, A.R.; Cranfill, R.; Wolf, P.G.; Hunt, J.S.; Sipes, S.D. 2001: Horsetails and ferns are a monophyletic group and the closest living relatives to seed plants. Nature 409: 618–622.
Pryer, K.M.; Schuettpelz, E.; Wolf, P.G.; Schneider, H.; Smith, A.R.; Cranfill, R. 2004: Phylogeny and evolution of ferns (monilophytes) with a focus on the early leptosporangiate divergences. American Journal of Botany 91: 1582–1598.
Smith, A.R.; Pryer, K.M.; Schuettpelz, E.; Korall, P.; Schneider, H.; Wolf, P.G. 2006: A classification for extant ferns. Taxon 55(3): 705–731.
Wagner, W.H. 1977: Systematic implications of the Psilotaceae. Brittonia 29: 54–63.
