Aponogeton natans (Linnaeus, 1771) Engler & Krause

Manawaduge, Chapa G. & Yakandawala, Deepthi, 2018, Morphometrics and taxonomic update to the Sri Lankan Aponogetonaceae, Phytotaxa 365 (3), pp. 201-224 : 213-214

2. Aponogeton natans (L.) Engler & Krause in Krause & Engler (1906: 11)

Saururus natans Linnaeus (1771: 227) . Type:— Koenig s.n. (holotype LINN 479.1!, isotype UPS).

Aponogeton monostachyon Linnaeus (1781: 214) .

Spathium monostachyon Edgeworth (1843: 533) . Type:—Edgeworth, Figure 16, Calcutta J. Nat. Hist. 1843

Tuber globule or obovoid,up to 2.3 cm Ø. Leaves floating or erect up to 16 × 3 cm; apex (narrowly) cuneate with a blunt tip and base cordate, mostly unequal, seldom cuneate; margin flat, Grooved midrib with 4–6 parallel veins (not prominent).Petioles up to 34 cm long, grooved. Submersed leaves absent. Peduncle up to 38 cm, not widening towards the inflorescence. Spathe up to 15 mm, caducous. Inflorescence with 1 spike up to 12 cm long, light purple, densely flowered, seldom laxly flowered, scentless, florets turned towards all directions. Tepals 2, spatulate, 1.8–3.0 × 1.0– 1.9 mm, purple, persistent, 1-nerved. Stamens 6, 2.0– 4.2 mm, filaments not widened towards the base, light purple, anthers dark purple. Ovaries 3, light purple, up to 4.0 × 1.6 mm, ovules c. 8. Infructescence up to 15 cm, very dense. Folicals up to 4.0× 1.6 mm, smooth and inflated with a very long (up to 1 mm) terminal beak. Seeds c. 1.9 × 0.7 mm with a double testa; outer one loose, winged, transparent and reticulately veined, inner one brown, closely fitting the embryo. Embryo c. 1.5 × 0.5 mm.

Phenology:— Flowering throughout the year. But flowering intensity increases just after the rainy season.

Distribution:— India, Pakistan and in the lowland dry zone of Sri Lanka.

Ecology:— Stagnant, shallow, most probably temporary waters, rice fields, ponds and marshes. Towards the edge of the larger water bodies. Occurring intermingled with other wetland plants during the dry season. Between 0–800 m elevation, mostly in open positions.

Uses:— Tubers and inflorescence are eaten.

Notes:— The populations encountered in Jaffna were occurring in the sandy soils in open areas.

Specimens examined:— SRI LANKA. Batticaloa District : Batticaloa, 25May 2014, Manawaduge & Yakandawala 704, 705, 706 ( PDA!) ; Batticaloa , 06 Dec. 2015, Manawaduge & Yakandawala 627 ( PDA!) ; Eravur , 8 Nov. 1969, Cramer 2750 ( PDA!, US) ; Hambantota District : Palatupana Tank near Palatupane Bungalow, 4 Dec. 1973, Sohmer 8999 ( P!, PDA!) ; Hambantota to Tissamaharama Road, mile marker 152/4, 19 Nov. 1973, Sohmer et al. 8854 ( PDA!, US) ; Ruhuna Nat. Park , block 1, Buttawa, 17 Nov. 1969, Cooray 69111701 R ( K, PDA!, US) ; Bundala sanctuary, 9 Apr. 1985, Jayasuriya & Balasubramanium 3299 ( PDA!) ; Ruhuna Nat. Park , c. 1 mile NW. of Yala Bungalow, 24 Nov. 1970, Fosberg & Sachet 52850 ( K, P!, PDA!, US) ; North of Kataragama in Ruhunu National Park Block 3, 23 Nov. 1968, Wirawan 640 ( PDA!) ; Mannar District : Murunkan, 14 June 2015, Manawaduge & Yakandawala 122 ( PDA!) ; Murunkan , 14 Jun. 2015, Manawaduge & Yakandawala 123 ( PDA!) ; Mannar , 12 Nov. 1970, Kundu & Balakrishnan 598 ( PDA!, US) ; c. 6 miles NE. of Mantai along the road to Pooneryn, near mile marker 12, 7 Dec. 1974, Davidse & Sumithraarachchi 9171 ( PDA!, US) ; Polonnaruwa District : Somawathiya, 25 Oct. 2014, Manawaduge & Yakandawala 113 ( PDA!) ; Puttalum District : Wilpattu National Park, 2 miles north of Marai Villu, 1 Feb. 1970, Cooray 70020106 R ( PDA!) ; Vavunia District : Muliyarkulam, 14 Jun. 2015, Manawaduge & Yakandawala 121 ( PDA!) ; Chandakulan Tank , 18 miles. NE. of Puliyankulam, 9 Dec. 1970, Fosberg & Balakrishnan 53479 ( K, PDA!, US) .