Potamogeton maackianus A.Benn.

Vertical shoot continuously growing, aseasonal, specialised turions not produced; stem slender, terete, much branched; horizontal shoots short, not much differentiated. Floating leaves absent; submerged leaves linear to lanceolate, sessile, lamina 20-80 by 2-4 mm, 3(-5)-veined, with 4-8 inconspicuous sclerenchymatous strands, margin fine-ly serrulate, base rounded, apex obtuse to truncately acute; stipules adnate, convolute, 4-12 mm, fused to the leaf for 2-6 mm. Spikes suborbicular or cylindrical, contiguous or shortly distant, 5-10 mm; peduncle 10-30 mm, often in an umbel-like arrangement at the top of the vertical shoot. Flowers 2-4, with 4 carpels. Fruits broadly ovate-elliptic, c. 3 mm, acutely keeled, beak short. Stem anatomy: Stele of oblong type. Endodermis of O-type. Interlacunar bundles absent, subepidermal bundles present. Pseudo-hypodermis present, 1-layered. Chromosome number: 2n = 52.