Lygodiaceae.
Many sources put the Lygodium genus in the Schizaeaceae family but others (including Mabberley) feel
it is different enough to warrant its own family Lygodiaceae.
Lygodium, with 26 species is the only genus in the family.
There are 4 species in North and North-eastern Australia.
Lygodium microphyllum is deciduous and all the pinnule stalks are the same length.
In Lygodium flexuosum and L. japonicum the pinnule stalks get shorter towards the tip of the pinna and they are not deciduous.
The fronds of L. flexuosum are bipinnate while those of L. japonicum are tripinnate.
Lygodia are climbing vines that grow from creeping rhizomes with fibrous roots.
They climb by scrambling over vegetation and by twining.
They can grow quickly and smother other vegetation.
What looks like a long stem with leaves is actually a single frond that continues to grow and can reach 15 or even 30 m in length.
Fronds are sometimes described as leaves.
Rhizomes, stems and pinnae (leaflets) can all have hairs.
Each frond consists of a thin, wiry midrib or rachis that can be green or reddish.
One side is flattened with a ridge on each side.
Primary pinnae branch off the rachis alternately.
The pinnae stalks may be of equal length along the rachis or get smaller towards the end.
The primary pinnae divide into secondary pinnae and these sometimes divide into tertiary pinnae
(terminal pinnules or ultimate segments).
Pinnae vary in shape and size and in whether the veins anastomose or not.
The sterile and fertile pinnae may be similar or different.
Sori are on the lower surface of the ultimate segments of fertile pinnae.
Each contains a sporangium protected by a flap of tissue like the indusium of other ferns.
Spores are produced in the sporangia.
J.F.
