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Cystodiaceae

Terrestrial ferns of moderate size, stout, erect to ascending radial caudex, dictyostelic with a solid central sclerotic strand, apex and young parts covered with long, fine, mutiseptate, golden hairs. Fronds long-stipitate, the stipe with vascular bundles in 2 lateral arcs concave laterally, uniting near the insertion of the frond to form an X-shaped strand, then abruptly separating to form 2 dorsiventral bundles, rachis and stipe adaxially grooved and ridged, not continuous with the grooves of higher order axes; lamina bipinnate, basally truncate, catadromous, fertile pinnules slightly narrower and with larger teeth than sterile; veins in pinnules pinnately arranged about a prominent costule, free, simple or forked. Sori submarginal, terminal on the veins, protected by a reflexed lobe of the lamina (outer or false indusium) and a thinner, smaller, cupped, inner indusium attached at the base of the receptacle; sporangia with a slightly oblique to almost longitudinal annulus, interrupted by the pedicel; paraphyses numerous, simple, multiseptate, nonglandular. Spores globose, trilete, granular.

Distribution

A family of a single genus ranging from Borneo through New Guinea and the Bismarck Archipelago to the Solomon Islands. The specimens from Bougainville and the Solomon Islands represent a distinct subspecies.

Literature

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

Holttum, R.E. 1963. Cyatheaceae. Fl. Males. ser. 2, 1: 65 - 176.

Genera

A monogeneric family ... Cystodium (1)

Note

This genus has until recently been included in the Dicksoniaceae allied to Dicksonia or in the Cyatheaceae by those authors favouring a wide concept of that family. Recent studies (Croft 1986) have shown that there are significant differences in the internal stipe anatomy, correlated with other differences in morphology, anatomy, spores, chromasomes, and ecology that justifies the elevation of Cystodium to the rank of family.


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