Pteridophytes (Spore Producing Plants: Ferns and More) • Earth.com

Whisk fern

(Psilotum complanatum)

galery
en

Description

Psilotum complanatum, the flatfork fern, is a rare herbaceous epiphytic fern ally in the genus Psilotum. There is some evidence that it might be a true fern that has lost some typically fern-like characteristics. Morphologically, the plant is simple, lacking leaves and roots, and having hanging stems with dichotomous branching, which lack developed leaves but have minute scales. The stems and branches have protostele, with a triangular-shaped core of xylem. The scales are arranged in two rows along the flat stems and branches. The stems are broadly triangular in cross section and 5 mm wide. The branches are 1.5 to 2 mm wide. P. complanatum grows 10 to 75 cm long and stems branch in pairs a number of times up their length and are covered with brownish colored hair-like rhizoids. Small stalks end with simple sporangia from the axils of minute bifid, rounded sporophylls. Bean shaped, monolete spores are produced. The spores germinate best in a dark environment when ammonium is present. The gametophyte is non-photosynthetic, living in association with a fungus for its nutritional needs. Plants grow from a subterranean rhizome which anchors the plant in place and absorbs nutrients by means of filament like rhizoids.

Taxonomic tree:

Domain:
Kingdom: Plantae
Phylum: Psilophyta
Class: Psilotopsida
Order:Psilotales
Family:Psilotaceae
Genus:Psilotum
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