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Acrostichum (family Pteridaceae) A genus of ferns in which the rhizome is creeping, the leaves are pinnate, and the upper pinnae are reduced and covered below by sporangia (the ‘acrostichoid’ condition, which also evolved independently in other ferns). There are 3 species in mangrove forests throughout the tropics (A. aureum is the commonest). Its young leaves are edible.