Azolla rubra

Salviniaceae

Azolla rubra R.Br.

Link to Australian Plant Name Index for publication details and synonyms: https://id.biodiversity.org.au/name/apni/115407

Free-floating, aquatic ferns. Stem short, creeping, bearing short roots and sometimes trichomes. Leaves small, imbricate, fleshy; margins transparent, bilobed; upper lobe 1–2 mm long, usually minutely to strongly papillate, lacking veins, containing the cyanobacterium Anabaena azollae in central cavity; lower lobe submerged and bearing 2–4 megasporangia or microsporangia in axils. Megasporocarps oblong-conical, protected by a membrane-like indusium; megaspores solitary; basal portion rounded, smooth, pitted or with raised, hexagonal markings surmounted by 3–9 floats. Microsporocarps ovoid to globular, covered by a transparent indusium; microsporangia 7–100, spherical, stalked, containing 4–10 massulae bearing few to many, hooked or non-hooked, septate or non-septate processes. Microspores 32–64, in groups within massulae. 

Plants ovate in outline, branching irregularly; roots simple. Leaves triangular; apex rounded; margins membranous and translucent; surface smooth, bright red or green. Microsporangiate massulae spherical, prominently barbed on all surfaces. Megasporocarps brown, partially obscured by leaf lobe. Megasporangia each with 3 apical swimming floats.

Widely scattered across Australia, mostly in temperate and subtropical areas and in man-made habitats. Also widespread outside Australia.

Free-floating aquatic fern occurring on still or slow moving water, particularly man-made dams and ponds.

Plants irregularly branched, roots simple = Azolla rubra

Plants regularly branched, roots feathery = Azolla pinnata