indusium

Sori hemispheroid, in 2-3 series on each side along the costules, without indusium.

囊群圆形，沿中脉两侧各排成2-3行，无囊群盖。

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

是一种起源于胎座（为叶表皮译者注）瓣片状组织，覆盖在蕨类植物囊群中正在发育囊上。