Definition of sorus in US English:



  • 1A cluster of spore-producing receptacles on the underside of a fern frond.

    • ‘They are commonly referred to as the Lip Ferns because the sori are borne at the margins of the pinnules and the leaf margins themselves are often reflexed to form false indusia that protect the sori.’
    • ‘At flowering, the fungus undergoes massive sporulation in the floral tissue and replaces the seeds with smut sori.’
    • ‘These, when the humidity drops, pop the sori open with a spring like movement, casting the tiny spores all over the place.’
    • ‘In fertile plants, sori are produced on the abaxial side of the leaves in summer.’
    • ‘Viewed through a microscope, you can see that a single sorus is actually a complex structure.’
    1. 1.1 A gamete-producing or fruiting body in certain algae and fungi.


Mid 19th century: modern Latin, from Greek sōros ‘heap’.