Tên Khoa học: PetrosaviaTên tiếng Anh: Tên tiếng Việt: Vô diệp liênTên khác:
Perennial mycoheterotrophic, whitish, pale yellowish or creamy (brownish when dried), glabrous herbs. Rhizome scaly, slender. Leaves scaly, membraneous, ovoid to deltoid, with more or less attenuate tip and a sheathing base, and entire margin. Lower leaves densely arranged, appressed to stem; upper leaves distant, loose. Inflorescence a raceme or corymb/umbel, terminal, bracteate and bracteolate. Flower-subtending bracts lanceolate, longer or equal to pedicels in the older buds and beginning of anthesis but much shorter in fruits due to pedicel elongation. Bracteoles well-detectable, located at the pedicel base, shorter than flower-subtending bracts. Flowers erect, bisexual. Perianth biseriate, persistent; tepals 3 in each whorl, erect in the beginning of anthesis, spreading in fruits, the outer tepals 1.5–2.0 times shorter and much narrower than the inner, do not touch each other in bud, the inner tepals erect, inserted higher up than the outer, deltoid-triangular, valvate. Stamens 6, shorter than the inner tepals; outer stamens slightly fused to carpels and inner ones fused to inner tepals by their filament bases; filaments subulate; anthers ovoid, basifixed, dithecal, tetrasporangiate. Carpels 3, sessile, united up to 1/2 of the ovary length. Ovary semi-inferior, 3-locular in syncarpous region; ovary bowl as long as inner tepals at anthesis. Styles short, recurved or more or less erect, hollow, sealed by secretion in their upper part; stigmas capitate, facing outwards. Septal necta- ries interlocular. Ovules numerous, with funicular obturator. Capsule hemisyncarpous, follicular; each carpel dehiscing along ventral slit and dorsal vein. Seeds brownish, elliptic to oblong, with a hyaline wing around the seed body, numer- ous, dusty, longitudinally striated, embryo minute and underdifferentiated. The genus Petrosavia has two species distributed in Japan, China, Taiwan, Myanmar, Thailand, Vietnam, Malaysia, Indonesia. Within the territory of Vietnam, both of them are reported. The species of this genus occur on forest floor at 0–2300 m a.s.l.