Compilation
Potamogeton livingstonei

Rooted submerged aquatic with adventitious roots at the nodes of the horizontal shoots; rhizomes perennial, slender to very robust, terete, whitish, sometimes developing tubers filled with starch and surrounded by a scaly leaf at the end of the growing season (such tubers generally absent in tropical plants); stems annual to perennial, up to 4 m long and 0.5– 2 mm in diameter, filiform to relatively robust, terete, sometimes pink, usually richly branched. Submerged leaves bright green to olive green, sessile, (20– )30– 125(– 300) mm long, 0.2– 4 mm wide, 24– 200 times as long as wide, linear, canaliculate or flattened, straight at base, entire at margins, the narrower leaves acute to finely acuminate at apex, sometimes the broader leaves obtuse and mucronate; midrib bordered on each side by one to several air channels, lateral veins 1– 2 on each side, inconspicuous; stipules persistent, fused with the leaves for 8– 70 mm, forming a convolute and winged leaf base, ending in a free hyaline ligule, (3– )5– 15 mm long, obtuse, rounded or truncate, later disintegrating into fibres; intravaginal scales 0.4– 0.6 mm long; floating leaves always absent. Peduncles 20– 100(– 450) mm long, 1.5– 5(– 10) times as long as the fruiting spike, as thick as the stem, flexuous; spikes (4– )8– 14-flowered, with 2– 7 pairs or whorls of flowers, contiguous at first, later distant, or the upper groups ± contiguous, 13– 35(– 60) mm long when in fruit. Tepals orbicular to elliptical, 1– 3 mm long; anthers 0.8– 1.3 mm long; carpels 4; stigmas borne on a short but distinct style. Fruitlets brown,(2.5– )3.3– 4.7(– 5.1) mm long, 2– 3.6 mm broad, asymmetrically obovoid, ventrally nearly straight, dorsally very convex, hardly 3-keeled; beak 0.2– 0.6 mm long, ventral, rarely subventral. Stem anatomy: stele of four bundles, mostly oblong; endodermis of U-type; interlacunar bundles present (in 1 ± complete ring); subepidermal bundles few or absent; pseudohypodermis present, 1-(– 2)-layered. Fig. 2 (p. 6).