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（应为叶表皮译者注）瓣片状组，在蕨类植物囊群中正在发囊上。

Quillworts are heterosporous, mainly aquatic perennials, with a dense rosette of tubular quill-like leaves arising from a short, stout rootstock.

水韭目植物具有异型，是多年水生植物。其管状条形叶密集簇生于粗短根茎之上。