Definition of "perigonium" []

• The sterile parts of a flower; collectively, the sepals and petals (or tepals); the perianth. (noun)
• The modified leaves around the antheridia in a bryophytic plant. (noun)
• The wall of the sporosac in a hydroid. (noun)

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• "At the top of the axis in the male plant rise the antheridia, surrounded by an envelope of modified leaves called the perigonium."