A very small tongue-shaped flap of tissue inserted on the upper surface of the leaves (microsporophylls) and sporophylls of certain clubmosses (e.g. Selaginella) and quillworts (Isoetes).

• 某些石松门（如卷柏）和水韭类植物（水韭属）的孢子叶上具有的一种极小的舌状结构，。