Dicksoniaceae
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- Related Topics:
- tree fern
Dicksoniaceae, the tree fern family, containing about 3 genera and some 30 species, in the division Pteridophyta (the lower vascular plants). The family has a long and diverse fossil record extending back to the Triassic Period (251 million to 199.6 million years ago). Members of Dicksoniaceae are widely distributed and a common component of humid tropical forests around the world. Most Dicksoniaceae species are notable for their trunklike stems, which are rhizomes modified for vertical growth and embedded in a thick mantle of adventitious roots. The leaves, which are often highly divided, may be several metres long and are notable for the absence of scales and the presence of often conspicuous multicellular hairs, especially on the petiole. The sori are circular to elliptic in outline and occur along the edges of the leaf segments. They are protected on one side by the modified curled leaf margin and on the other by a membranous protective flap (indusium), which results in the appearance of a cuplike to boxlike covering for the sporangia. The spores are globose (tetrahedral).
Lophosoria quadripinnata, once assigned to its own family (Lophosoriaceae), is now assigned to Dicksoniaceae. The plant is widespread in Neotropical mountains, from southern Mexico to Bolivia and Brazil. It also occurs on some islands, including Cuba and the Juan Fernández Islands. L. quadripinnata is a small tree fern with highly divided leaves. The round sori lack an indusium. The spores are globose and have a conspicuous donut-shaped flange around the circumference.
