Scientific name: Potamogeton perfoliatus L.
Common name: Perfoliate Pondweed
Description
Habit: Aquatic perennials. Hybrids are rather frequent in this genus.
Leaves: Leaves mostly alternate, some opposite, submerged, subtending inflorescences, all with membranous sheath or stipules; submerged leaves usually triangular-oval, but sometimes lanceolate, acute or obtuse, clasping the stem with a broad, deeply cordate base, up to 11.5 x 4.2cm (often much shorter); stipules small, decaying early, membranous.
Flowers: In spikes or heads; spike 15-25mm; peduncles longer, scarcely swollen at the top; usually borne above the water-surface; perianth of 4 free, greenish segments; carpels usually 4, free; stamens 4, anthers stalkless, attached to the base of the adjoining perianth-segment.
Fruits: Drupes or achenes, 1 or more present, 2.6-4mm, brownish-green, with thick pericarp, soft on outside but with bony inner layer.
Habitat: Lakes, streams, ditches and canals.
Distribution: Frequent.
Native status: Native
Of conservation interest: No