Japanese name: アカウキクサ（赤浮草） Scientific name:Azolla imbricata
[Overview]
A small aquatic fern found in rice paddies and lakes, floating on the water surface.
The plant body is reddish and triangular, 1–1.5 cm long; the roots hang down into the water and have long root hairs.
The stem branches densely in a pinnate manner, and the leaves are densely arranged alternately in two rows.
The leaves are triangular-round, 0.15 cm long, and divided into upper and lower lobes; like the stem, they are densely covered with granular projections, and the margins are translucent and membranous.
The leaves are green in summer but turn bright crimson in winter.
The upper lobe of the leaf floats on the water surface, and in the cavity at its base lives Anabaena, a kind of cyanobacterium capable of nitrogen fixation, in symbiosis.
The lower lobe of the leaf sinks into the water, and the sporangia clusters are borne between the submerged leaves; there are two types, megasporangia clusters and microsporangia clusters.
The sporangia clusters mature from autumn onward, and the megaspores have floating organs.
