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Psilotaceae

Incl. Tmesipteridaceae

Small to moderate-size terrestrial or epiphytic herbs (Tmesipteris apparently restricted to Dicksonia), rhizome shortly creeping, dichotomously branched, protostelic, lacking roots, densely covered with fine rhizoids. Stems triquetrous, rigid and erect, to flattened or +/- terete, flaccid and pendulous, photosynthetic, linear, simple towards the base, in Tmesipteris mostly simple throughout sometimes bifid upwards, in Psilotum repeatedly dichotomous upwards, siphonostelic, leaves (sterile lateral appendages) simple, minute, scale-like, lacking a midrib, at the basely only in Tmesipteris, scattered along the stem in 2 or 3 rows in Psilotum, Tmesipteris for the most part with spiral or distichous flattened leaf-like apiculate appendages each with a single vein, these appendages bifid when fertile. Synangia globular, 3-lobed, composed of 3 fused sporangia, borne in the axils of minute, scale-like appendages in Psilotum, or elongate, 2-lobed, composed of 2 fused sporangia in Tmesipteris, exindusiate, homosporous, each lobe bivalvate, dehiscing by a radial slit. Spores monolete, finely reticulate.

Distribution

A bigeneric tropical, subtropical and southern temperate family with c. 12 species. In Papuasia represented by both genera and 3 species.

Literature

Braithwaithe, A.F. 1973. Tmesipteris in the Solomon Islands. Brit. Fern. Gaz. 10: 293 - 303.

Johns, R.J. 1981. The ferns and fern allies of Papua New Guinea. Part nine: the Psilotaceae. P.N.G. Univ. Tech. Res. Rep. R48-81: 1.1 - 1.7.

Genera in Australia and Papuasia

1

Terrestrial or epiphytic, stems triquetrous or flattened, several-times dichotomous, bearing minute scale-like leaves; synangia 3-lobed

Psilotum (2)

Epiphytic, nearly always on Dicksonia, stems +/- terete, simple or less often bifid, bearing flattened leaf-like appendages; synangia 2-lobed

Tmesipteris (1)

Note

Some authors separate Tmesipteris into its own family, Tmesipteridaceae. Although the two genera are morphologically very distinct, cytological evidence does not support this separation (Brownsey et al. 1985).


Updated November 1999 by Jim Croft (jim.croft@environment.gov.au)