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Family :

Azollaceae

Division :

Ptedophytes

Description


An aquatic fern-allies. Rhizome slender branching alternately, zigzag, branched bearing rhizoids and lamina, rhizoids hang down in water. Fronds inhabit an endophytic cyano bacterium Anabaena azollae. Lamina in to two alternate rows, bilobed, one floating and another submerged. Floating lobe over lapping the rhizome, upper floating sessile lobe covered with papillae, turning reddish in winter, with a cavity near the base containing  an algae Anaebaena  azollae.The submerged lobe only one cell thick. Sorus on submerged lobes near the bases of the branches, enclosed by indusia each containing spores of two types, one megaspores and  numerous microspores. Sori on the submerged lobes.