British ferns (Filicopsida)
Sporophyte. The rhizomes becoming very stout; ascending to erect; without scales, hairy; becoming trunk-like beneath the crown of leaves, potentially to several meters high, covered with the blackened, persistent petiole bases and matted on the lower part with fibrous roots.
Leaves spectacularly aggregated terminally (conspicuously spirally arranged); to (80–)100–200(–300) cm long (and to 60 cm or more wide); persistent; complexly divided; tripinnate with conspicuously divided ultimate pinnules. Pinnae about 25–45 on each side of the leaf. The petioles densely covered with 2–4 cm long reddish or red-brown hairs shorter than the blades; vascularised via a single strand (basally, via a broad, gutter-shaped leaf trace), or vascularised by several discrete strands (the basal bundle breaking up distally into numerous small bundles). Leaf blades in outline elliptic. The longest pinnae around the middle of the blade to above the middle of the blade. The pinnae decreasing markedly in length towards the base of the blade, the basal ones relatively short. The venation of the lamina open (the branches reaching the margins of the segments).
The sporangia marginal; aggregated in sori. The sori about 1 mm in diameter, usually four, one on each lobe of the ultimate pinnules; remaining discrete at maturity; with a true indusium, or protected by true and false indusia combined (these constituting the globular, bivalved, ostensible indusium, which becomes hard at maturity). The false indusia interrupted on the individual blade segments (i.e., accommodating the discrete sporangia in combination with the true indusium). Paraphyses present in the sporangia. The sporangia developing sequentially within a sorus; developing sequentially in the gradate sorus, with a vertical annulus. The mature spores monolete; without a perispore.
Distribution and habitat. In moist woods and shady situations. Naturalized. Native to S and SE Australia, naturalized in S Kerry, Cornwall and also in the Isles of Scilly, where a control program is in operation.
Vice-county records. Britain: West Cornwall, East Cornwall. Ireland: South Kerry.
Classification. Family Dicksoniaceae; Dicksoniaceae (Stace).
Illustrations. • Dicksonia antarctica (photo).
To view the illustrations with detailed captions, go to the interactive key. This also offers full and partial descriptions, diagnostic descriptions, differences and similarities between taxa, lists of taxa exhibiting or lacking specified attributes, and distributions of character states within any set of taxa.
Cite this publication as: ‘Watson, L., and Dallwitz, M.J. 2004 onwards. British ferns (Filicopsida). Version: 4th January 2012. http://delta-intkey.com’.