Potamogeton drummondii
Benth.Emergent herb; branches flattened, up to c. 4 m long. Leaf sheath free, up to 4 cm long; ligule absent. Submerged leaves different from emergent ones. Submerged leaves thin and translucent, sessile or shortly petiolate; lamina lanceolate, 3–10 cm long, 0.5–2.3 cm wide; base rounded or acute; margin flat or undulate; apex obtuse or tapered; 5–15 principal longitudinal veins, with finer transverse secondary veins; distal submerged leaves more like emergent leaves, but with petiole much longer than for emergent leaves. Emergent leaves floating ± thick and leathery, petiolate; lamina ovate to elliptic, 0.8–3.5 cm long, 1.0–1.5 cm wide, dull; base rounded or tapered; apex obtuse, acute or shortly mucronate; margin flat or slightly undulate; 5–16 principal longitudinal veins, with transverse secondary veins indistinct. Inflorescence c. 12–24 flowered. Infructescence 1.5–2.4 cm long (excluding non-fruiting part of axis). Fruiting carpels 2.1–3.0 mm long (including dorsal point), dorsal surface with a prominent, smooth to crenulate keel and 2 smooth lateral ridges, distally with a ± straight to curved point up to c. 0.7 mm long. Flowers and fruits Sep.–Apr.
VVP, GipP, EGL, HNF, VAlp. Also WA, SA, Qld, NSW, Tas. Occurs in still or slow moving fresh water, in dams, swamps and creeks on muddy substrates.
Potamogeton drummondii is widespread in Western Australia, with a few isolated records in eastern Australia. This species closely resembles P. cheesemanii, that is much more common and widespread in south eastern Australia. The difference between the two species appears to be very slight. Emergent leaves are less than 1.5 cm wide, often with fewer than 10 veins, and usually quite round in P. drummondii, while those of P. cheesemanii are greater than 1.5 cm wide, with greater than 10 veins, and typically ovate. Based on these characters, much of the Victorian material of P. drummondii can be assigned to either of these two species. Further study is required to determine the distinction of these species, and their distributions. It is possible that P. drummondii is absent in eastern Australia, or that different names have been applied to the same taxon in eastern and western Australia.
