perigonium
/ˌpɛrɪˈɡəʊnɪəm/noun
1The perianth of a flowering plant.
2A cluster of modified leaves surrounding the antheridium of a bryophyte.
Origin
Early 19th century; earliest use found in Patrick Keith (1769–1840). From scientific Latin perigonium from peri- + ancient Greek γόνος offspring, seed + scientific Latin -ium.