Blechnum cartilagineum.
Gristle Fern. Family Blechnaceae.
A hardy terrestrial fern endemic in parts of Australia including Queensland.
When mature they can look like a small tree with a trunk up to 30 cm high with arching fronds forming
a rosette at the top.
The rhizomes, creeping or sometimes in the form of an erect trunk, are black and sometimes have the
bases of old fronds attached.
They are densely covered in thin, triangular, black scales up to about 1.5 cm long.
Frond stalks are up to 70 cm long, black at the base and pale brown above.
The upper part is smooth with a few scales but the base has many scales similar to those on the rhizome.
The main midrib of the frond is grooved above, pale brown with a few scales.
The pale to dark green fronds are usually 50 to 100 cm long but occasionally up to 200 cm.
New fronds have a pink tinge.
Sterile and fertle fronds are usually similar although the fertile segments can be narrower.
The ovate frond lamina is dissected, almost down to the midrib, into up to 50 alternately arranged segments.
The segments are linear to lanceonate, up to 15- 20 cm long and 10 mm wide.
Most have no stalk but are attached to the main midrib by their widened bases which may be continuous
with those of adjacent segments.
The lower segments can be on short stalks, separate and bent downwards.
There are 3 longitudinal veins with in each segment.
The segment margins are finely toothed.
Sporangia form narrow, continuous rows either side of the midrib and have linear indusia which
open towards the midrib.
J.F.
