Aponogeton jacobsenii Bruggen (1983: 120)

Manawaduge, Chapa G. & Yakandawala, Deepthi, 2018, Morphometrics and taxonomic update to the Sri Lankan Aponogetonaceae, Phytotaxa 365 (3), pp. 201-224 : 215-216

5. Aponogeton jacobsenii Bruggen (1983: 120)

Type:— Hoogland 11525 (holotype L, isotypes CANB, E, PDA!, US).

Tuber cylindrical and elongate; up to 4 cm Ø and 5 cm long, covered with long thin roots. Submerged leaves lamina; 7–19 × 3.1–7.0 cm; ovate to rounded triangular, leathery, apex acute and base cordate, margin undulate, Protrude midrib with 6–8 parallel veins. Petioles up to 18 cm long, brittle, bluntly triangular. Immature leaves are purple to maroon, turn to bright green with maturity. Floating leaves absent. Peduncle up to 55 cm, not widening towards the inflorescence. Spathe up to 2.5 mm, caducous. Inflorescence with 1 spike up to 11 cm long, dark pink and white, densely flowered, florets turned towards all directions. Tepals 2, broad, 1.2–2.3 × 1.3–2.5 mm, white, persistent, 1- nerved. Stamens 6, 1.0– 1.4 mm, filaments strongly widening towards the base and swollen, white, anthers dark purple. Ovaries 3, dark pink when mature, 1.7–1.8 × 2.3–2.5 mm, ovules 2. Infructescence up to 15 cm, dense. Folicals up to 15 × 10 mm, elongated, triangular, with smooth coat and a short, terminal, curved beak. Seeds with a simple testa, thick and transparent. Embryo up to 13 × 8 mm, plumule attached at the middle of the embryo and in a very wide groove.

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

Distribution:—Horton Plains.

Ecology:—In slow moving streams of the Horton Plains and in small pools fed by seasonal springs, in Pattipola area.

Uses:— Inflorescences have been eaten in the past.

Notes: —Even though the plant has been occurring in abundance in the past in the Nuwara-Eliya district including the Greogry lake, now they are confined to the Horton Plaines and very few isolated patches in the Pattipola area. Aponogeton jacobsenii is described as a species with floating leaves, but the occurrence of floating leaves are said to be very rare ( Bruggen 1985) and rare ( Bruggen 1987). However, during our extensive field studies for 4 years, we have never encountered floating leaves in A. jacobsenii and therefore in the present study it is described as a species with no floating leaves. The illustration of A.jacobsenii given in the Handbook to the Revised Flora of Ceylon ( Bruggen, 1987) cites a drawing with two floating leaves, but this is a mistakenly cited drawing of A. crispus with two floating leaves as A. jacobsenii was initially identified as a A. crispus ( Bruggen 1985) .

Specimens examined:— SRI LANKA. Badulla District : c. 0.5 mile N. of Pattipola, 10 Mar. 1969, Hoogland 11525 ( CANB, L, PDA!, US) ; Nuwara-Eliya District : Horton plains, 13 Oct. 2014, Manawaduge & Yakandawala 112 ( PDA!) ; Horton plains , 23 July 2015, Manawaduge & Yakandawala 124 ( PDA!) ; Ohiya Creek 17 May 1968, Mueller- Dombois 68051706 ( PDA!, US) ; Horton Plains , growing in streams at the bottom of hill near a small broad water falls below Farr Inn., 24 May 1969, Read 2051,2052 ( PDA!) ; Hakgala Botanic Gardens , 9 Mar. 1969, Hoogland 11519 ( CANB, PDA!, US) ; From Farr Inn to World’s End, 6 Oct. 1973, Waas 119 ( L, PDA!, US) ; Nuwara Eliya Lake , 18 Sept. 1969, v. Beusekom 1446 ( L, PDA!, US) ; Farr Inn , 17 Oct. 1974, Davidse 7616 ( K, L, PDA!)