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

是种起源于胎座（应为叶表皮译者注）的瓣片状组织，覆盖在蕨类孢囊群中正在发育的孢囊上。

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

水韭目的具有异型孢，是多年水。其管状条形叶密集簇于粗短的根茎之上。