A nonflowering plant of the phylum Filicineae having creeping or erect rhizomes
and large conspicuous leaves. ferns are characterized by their alternation
of generations: the conspicuous sporophyte,
which possesses leafy fronds, stems, rhizomes,
and roots and reproduces by minute spores
usually clustered on the leaves; and the inconspicuous gametophyte,
which resembles moss and produces gametes (sperm and ova). Fronds unroll
from curved "fiddle-heads" and may be divided into leaflets.
|A fern growing on the trunk of a Sabal palm in Florida.
Sunlight passing through the fern's frond highlight the many spore-containing
sori. Source: NBII image gallery
Ferns were growing in the Devonian period,
some 400 million years ago. They are widely distributed throughout the world,
but the majority grow in the tropics. About 10,000 species have been identified.
The best-known genus Pteridium (bracken) grows on moorland and
in open woodland.