1. Blyxa Noronha ex Thouars, Gen. Nov. Madagasc.: 4 (1806).
Taxon Description
Annual or perennial, submerged aquatic herbs. Roots adventitious, unbranched. Stems either elongate, erect and floating or horizontal and stoloniferous or simple corm. Leaves submerged, all basal or inserted spirally along the stem, elongate sessile, linear, usually with a distinct midrib and numerous thin secondary and tertiary parallel veins. Stipules absent. Inflorescences basal or axillary, peduncle bearing a spathe enclosing a usually single flower. Spathe 2–6-nerved. Flowers actinomorphic, unisexual or bisexual. Sepals 3, free, tubular during anthesis, persistent. Petals 3, free, white. Stamens 3 in bisexual flowers, 6 or 9 in unisexual flowers; filaments filiform; anthers 4-loculed, basifixed, dehiscing latrorsely. Ovary inferior, 3-carpellate, long-beaked above; ovules many, placentation parietal; stigma 3-lobed, fused below into long style. Fruit a linear capsule disintegrating at maturity. Seeds numerous, ellipsoidal or fusiform with variously ribbed and tubercled, sometimes with spiny appendages at end.
Taxon Statistics
Worldwide 12 species in tropical and subtropical regions. Three species in Nepal.
Key to Species
1a Stems elongate. Leaves cauline ………………………………………………………………………………………………..………………… 3. B. japonica
b Stems shortened or absent. Leaves basal …………………………………………………………………………………………………………………….. 2
2a Seeds without a projection, with smooth surface ……………………………………………………………………….…………….… 1. B. aubertii
b Seeds with filliform projection from each end, with prominent acute spines on surface………………… 2. B. echinosperma
1. Blyxa aubertii Rich., Mem. Cl. Sci. Math. Inst. Natl. France 1811(2): 19 (1814).
Blyxa graminea Steud.; Blyxa oryzetorum (Decne.) Hook.f.
Annual, submerged herbs, 4–15 cm. Roots adventitious. Stems shortened. Leaves in basal rosette, translucent, linear, 2–8 cm X 2–3 mm, apex acuminate, midrib conspicuous, finer longitudinal veins connected by numerous transverse veinlets. Spathes tubular, laterally somewhat flattened, 6-nerved, green, 3–5 cm X ca. 2 mm; peduncle 2.7–8 cm. Flowers bisexual, solitary. Sepals green, linear-lanceolate, hooded, 5–7 X ca. 1 mm. Petals white, linear, 9–17 X ca. 0.5 mm. Stamens 3; filaments 3–6 mm; anthers 1–1.8 mm, dehiscing before the stigmas emerge from the calyx tube. Ovary narrowly cylindric, 2.5–4 cm; styles stout ca. 7 mm. Fruit a capsule, terete or cylindrical, (2–)4–6(–8) cm. Seeds 30–70, oblong-ovoid, 1.2–1.8 X ca. 0.6 mm, smooth.
Distribution: Nepal, W Himalaya, E Himalaya, Assam-Burma, S Asia, E Asia, SE Asia, Africa and Australasia.
Altitudinal range: 200–1700 m.
Ecology: Paddy fields and water channels.
Flowering: May─July. Fruiting: August─September.
2. Blyxa echinosperma (C.B.Clarke) Hook.f., Fl. Brit. India 5: 661 (1888).
Hydrotrophus echinospermus C.B.Clarke; Blyxa aubertii var. echinosperma (C. B. Clarke) C. D. K. Cook & Lüönd; Blyxa lancifolia Hook.f.
Annual, submerged herbs, 16–30 cm. Roots adventitious. Stems shortened. Leaves all in basal rosette, translucent, strap-shaped, 12–24(–40) cm X 4–8 mm, apex acuminate, midrib conspicuous, finer longitudinal veins connected by numerous transverse veinlets. Spathes tubular, laterally somewhat flattened, 6-nerved, green, 2–5 cm X ca. 2 mm; peduncle 2–12 cm. Flowers bisexual, solitary. Sepals green, linear, ca. 6 X 1 mm. Petals white, linear, 1–1.4 cmX 0.5–0.8 mm. Stamens 3; filaments 4–6 mm; anthers 1–1.8 mm, dehiscing before the stigmas emerge from the calyx tube. Ovary narrowly cylindric, 3–7 cm; styles 0.6–1.5 cm. Fruit a capsule, terete or cylindrical, ca. 7 cm. Seeds 30–50, fusiform or oblong-fusiform, 1.5–2 X ca. 0.8 mm, with filiform projections or ridges from each end, and with prominently acute spines on surface.
Distribution: Nepal, Assam-Burma, S Asia, E Asia, SE Asia and Australasia.
Altitudinal range: 700–2000 m.
Ecology: Paddy fields and water channels.
Flowering: June─August. Fruiting: September─October.
3. Blyxa japonica (Miq.) Maxim. ex Asch. & Gürke
Hydrilla japonica Miq. in Ann. Mus. Bot. Lugduno-Batavi 2: 271 (1866).
Perennial, submerged herbs, 10–20 cm. Roots adventitious. Stems elongated, usually branched below and simple above or contracted and rosette-forming. Leaves cauline, spirally arranged, lanceolate, 15–20 cm X 2–3 mm, apex obtuse, midrib distinct with very fine longitudinal veins. Spathes tubular, 2-nerved, green, 2–5 cm X ca. 2 mm, usually sessile or rarely with peduncle ca. 1.1 cm. Flowers bisexual, solitary or rarely paired in the spathe. Sepals green, linear-lanceolate, 2.5–5.5 X ca. 1.2 mm. Petals white, lanceolate, 3–10 X ca. 0.5 mm. Stamens 3; filaments ca. 2 mm, anthers 0.7–1 mm, dehiscing before the flower opens. Ovary conic, 2.5–5 cm; styles 3–4 mm. Fruit a capsule, terete, obclavate to obconical, 1–2.5 cm. Seeds 30-60, fusiform, 1–2.5 mm, smooth.
Distribution: Nepal, Assam-Burma, S Asia, E Asia and SE Asia.
Altitudinal range: 700–2000 m.
Ecology: Paddy fields and water channels.
Flowering: August─September. Fruiting: September─October.
Description of Blyxa japonica is based on the digital image of herbarium deposited at E. Similarly, description of flowers and fruit characters is based on other floras (Qingfeng et al. 2010), protologue text, and digital image of type (BM000958577).