Indusium The flap of tissue, derived from the placenta, that encloses the developing sporangia in the sorus of a fern.

• 囊群盖：是一种起源于胎座（应为叶表皮译者注）的瓣片状组织，覆盖在蕨类植物孢子囊群中正在发育的孢子囊上。