Synonyms: Maidenia APNI*
Description: Dioecious aquatic perennials or annuals with submerged leaves and floating flowers.
Leaves all basal or cauline and alternate, with sheathing bases.
Inflorescences axillary, unisexual, male spathes many-flowered, subsessile to shortly pedunculate; female spathes 1-flowered, with a long peduncle. Perianth in 2 whorls, the inner segments smaller. Male flowers released from the spathe, separating and rising to the surface; stamens 1–3. Female flower with 1-locular cylindrical ovary; stigmas 3, 2-fid; peduncle coiling on maturity, drawing developing fruit beneath the surface.
Fruit narrow-cylindrical, irregularly dehiscent; seeds numerous.
Distribution and occurrence: World: c. 16 species, cosmopolitan. Australia: c. 7 species (native), all States.
Text by S. W. L. Jacobs (1993); edited KL Wilson (March 2011)
Taxon concept: Les, Jacobs et al. (2008)
| | Key to the species | |
| 1 | Leaf tips obtuse; filaments in male flower fused for 75% of its length (hence Y-shaped); hairs absent from base of androecium; leaves 11–35 mm wide | Vallisneria australis |
| Leaf tips mostly acute; filaments in male flower free to fused for up to 75% of their length (hence V- or Y-shaped); hairs present at base of androecium; leaves usually 3–10 mm wide (occasionally to 15 mm) | Vallisneria nana |
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