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Dicksoniaceae

Incl. Culcitaceae, Thyrsopteridaceae

Terrestrial ferns, caudex massive, often erect, unbranched and tree-like, sometimes prostrate, radial, dictyostelic with large gaps corresponding to leaf bases, vascular tissue mostly surrounded by very hard sclerenchyma, growing apex protected by long reddish or golden mutiseptate hairs. Fronds short- or long-stipitate, the stipe bases usually persistent, vasculature of numerous small strands arranged in 3 arcs uniting upwards in various ways, lamina mostly bipinnate to 4-pinnate, veins free, mostly simple, or forked; fertile fronds sometimes contracted. Sporangia borne on receptacle at the ends of veins, the sorus indusiate, protected by a +/- cup-shaped inner indusium opening towards the margin and a reflexed marginal lobe of the lamina (outer indusium), the inner indusium thinner than outer indusium, or outer and inner indusium of similar texture and different from lamina, annulus +/- oblique, multiseptate paraphyses present; spores trilete, smooth or variously sculptured.

Distribution

A family of 5, possibly 6, genera and 45 species in the tropical and mostly southern temperate regions of the world. In Papuasia there are 4 genera with c. 11 species.

Literature

Copeland, E.B. 1949. Pteridaceae of New Guinea. Philip. J. Sci. 78: 5 - 40.

Croft, J.R. 1986. The stipe vasculature of the Dicksonioid genus Cystodium (Cystodiaceae). Kew Bull. (in press)

Holttum, R.E. 1963. Cyatheaceae. Fl. Males. ser. 2, 1: 65 - 176. Addenda 562 - 563 1981).

Genera

1a.

Upper surface of costae of ultimate leaflets raised, axes raised above, or if grooved the grooves not decurrent; fronds +/- elliptic in outline, 2 - 3-pinnate; rhizome an erect caudex, sometimes trunk-like

2

Upper surface of ultimate leaflets grooved, the groove decurrent into the groove of the supporting rachis; fronds deltoid in outline 3 - 4 pinnate; rhizome short-creeping

Culcita (2 - 3)

2a.

Outer indusium brown and quite distinct from the rest of the lamina

Cibotium (1)

Outer indusium green and not distinct from the rest of the lamina

3

3a.

Massive tree-ferns; fertile pinnules deeply lobed; pinna-rachis raised above

Dicksonia (c. 5)

Stem short and compact; fertile pinnules not lobed; pinna-rachis grooved above (Cystodiaceae)

Cystodium (1)

Note

This family has often been included with the Cyatheaceae (e.g. Holttum 1963, not 1981. Some authors remove Culcita and include it in the Thyrsopteridaceae with some New World genera, and others place it in its own family, Culcitaceae, separate from Thyrsopteridaceae and Dicksoniaceae.

The Old World species of Culcita have been placed in a distinct subgenus (Calochlaena) on the basis of significant differences in morphology and cytology that correlates with the very disjunct mid-Atlantic distribution of the remainder of the genus. It is very likely that further studies will show that the Papuasian subspecies should be raised to the generic level.

Recent studies (Croft 1986) show that Cystodium has a vascular anatomy significantly different from this group of genera and from Cyatheaceae; coupled with differences in spore anatomy, chromosomes, and morphology there is considerable evidence to place Cystodium in its own family (see Cystodiaceae).


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