Submitted by admin on April 23, 2009 - 00:42
Tree ferns are a conspicuous feature of the New Zealand vegetation; there are two genera: Dicksonia and Cyathea. Of Dicksonia there are three endemic species: (1) the widespread D. squarrosa, the silvery tree fern, which can produce stolons and thus colonise vegetatively; (2) D. fibrosa, with a mass of fibrous roots which sometimes form a trunk 2 ft in diameter; and (3) the woolly tree fern, D. lanata, which creeps on the ground. The genus Cyathea contains the largest and most beautiful tree ferns; there are eight species found here, four of them being common: (1) Cyathea medullaris, the black tree fern, or mamaku, with hexagonally marked black trunk, and black stemmed fronds up to 20 ft long; (2) Cyathea smithii is recognised by the light-brown stalks of dead fronds which persist and stand out round the stem like a ballet skirt; (3) the silver king, C. dealbata, easily recognised by the white-backed fronds; (4) the mountain tree fern, C. colensoi, which is semi-prostrate and lacks an indusium. There are two fine species found in Kermadec Islands. The genus Cyathea is distinguished from the genus Dicksonia by the presence of scales on the fronds; the latter has bristly hairs, moreover, the sori of Cyathea are round and away from the margin of the leaf, but in Dicksonia the sori are marginal with a two-valved indusium. The young fronds of Cyathea medullaris are beautiful as they first appear, tightly coiled, covered with large, shiny brown scales, and then as they gradually uncoil, still with these brown scales.