Acrostichum.
Most sources recognise 3 or 4 species with Acrostichum aureum and A. speciosum found in Queensland.
Mangrove, Swamp or Leather ferns are semi-aquatic plants that grow in wet ground among mangroves and in swamps, marshes and along creeks.
They need some fresh water when young but can survive in salty water and will grow in dense shade to full sunlight.
The perennial ferns form dense tussocks with erect then arching fronds up to 5 m long.
The rhizomes (underground stems) have large wide dark scales and there are strong prop roots.
The stalk or stipe is up to one third of the length of the frond.
The stipe has a grooved upper surface and can be smooth or have some scales or scale scars.
The lance-shaped to oblong blade is green above and paler underneath.
The lamina is pinnately divided into alternately arranged pinnae.
The lower pinnae are on a short stalk while the upper ones have no stalk and their base may run down the midrib.
There are no hairs and the veins form a network dividing the surface into narrow, slopping angular areas.
Only some fronds are fertile and, unlike other ferns the sporangia are not collected into clusters or sori but are scattered over the surface.
J.F.
