HYDROCHARITACEAE [Draft]

水鳖科  shui bie ke

Wang Qingfeng (王青锋)^[1]; Robert R. Haynes^[2]; C. Barre Hellquist^[3]

Herbs, annual or perennial, submerged or floating, aquatic, in freshwater or marine. Stems short or elongated, sometimes stoloniferous. Leaves radical or cauline, alternate, opposite, or whorled, sessile or petiolate, usually sheathing at base. Flowers unisexual or bisexual, actinomorphic, enclosed in a bifid spathe or within 2 opposite spathal bracts; spathes sessile or pedunculate. Perianth segments free, 1- or 2-seriate, 3 per series, outer often sepaloid, inner petaloid. Stamens 1 to many, occasionally some staminodal; anthers 2–4-thecous, basifixed, longitudinally dehiscent. Ovary inferior, 1-loculed; carpels 2–15, fused; ovules few to many, on parietal, sometimes intruding placentas; styles 2–5; stigmas usually bifid. Fruit a fleshy and berrylike capsule, dehiscent or opening by decay of pericarp. Seeds numerous, usually small, without endosperm; embryo straight.

Seventeen genera with about 80 species: widely distributed in tropical and subtropical regions of the world; nine genera and about 20 species in China.

[??possibly to move Najas here and add to key to genera.]

1a.     Marine herbs; pollen grains threadlike.

2a.    Plants slender; leaves usually opposite or binate, not in 2 rows, linear to ovate, usually petiolate      9. Halophila

2b.    Plants robust; leaves alterate, in 2 rows, ribbonlike, sessile.

3a.     Female inflorescence shortly pedunculate; leaves smaller, slightly falcate
................................................................................................................  4. Thalassia

3b.     Female inflorescence long pedunculate; leaves larger, not falcate ..................  3. Enhalus

1b.     Freshwater herbs; pollen grains not threadlike.

4a.    Leaves all basal; stems short.

5a.     Leaves linear, ribbonlike, sessile; fruit narrowly cylindric.

6a.     Stamens 3–9; ovary attenuate into a long, filiform beak; peduncle of female flower shorter  5. Blyxa

6b.     Stamens 1–3; ovary not as above; peduncle of female flower very long
.........................................................................................................  6. Vallisneria

5b.     Leaves lanceolate to orbicular, usually petiolate.

7a.     Stolon absent; leaves submerged; spathes usually winged ............................  1. Ottelia

7b.     Stolon present; leaves floating; spathes not winged ............................  2. Hydrocharis

4b.    Leaves cauline; stems elongated.

8a.     Leaves whorled.

9a.     Leaves distinctly serrate to unaided eye ..................................................  8. Hydrilla

9b.     Leaves minutely serrate, maginification needed ........................................  10. Egeria

8b.     Leaves alternate, opposite, or spirally arranged.

10a.   Flowers usually bisexual; sepals linear to lanceolate, shorter than petals; leaves with prominent midvein ..................................................................................................................  6. Blyxa

10b.   Flowers unisexual; sepals ovate, nearly equal to petals; leaves lacking a prominent midvein  7. Nechamandra

1. OTTELIA Persoon, Syn. Pl. 1: 400. 1805.

海菜花属  hai cai hua shu

Boottia Wallich.

Herbs, of freshwater. Stems usually cormlike. Leaves all basal, petiolate, usually sheathing at base; blades submerged or sometimes floating, linear to broadly ovate, 3–11-veined. Spathes elliptic or ovate, usually 2–6-winged, apex bifid or trifid, with 1 to many flowers. Flowers bisexual or unisexual and plants dioecious. Male flowers with longer pedicel. Bisexual and female flowers shortly pedicellate or without pedicel. Sepals 3, greenish, linear, oblong, or ovate. Petals 3, colored, orbicular to broadly obovate, much longer and wider than sepals. Stamens 3–15; filaments linear, flattened; anthers laterally dehiscent; staminodes (absent or 1–)3, often present in female flowers. Ovary of 3, 6 or 9 (or more) carpels; ovules numerous; stigmas 2 per style, linear. Fruit cylindrical, fusiform, or conical. Seeds numerous, small, often hairy.

About 21 species: tropical to temperate areas, about five species in China (two endemic).

1a.     Flowers bisexual.

2a.    Spathe with only one flower; flowers without gland; leaf sheath absent ......  1. O. alismoides

2b.    Spathe with many flowers; flowers with gland; leaves sheathed at base
..................................................................................................................  2. O. sinensis

1b.     Flowers unisexual.

3a.    Female spathe with 2–9 female flowers; styles 3; fruit triangular-cylindrical to fusiform  5. O. acuminata

3b.    Female spathe with only 1 female flower; styles more than 3, fruit oblong

4a.     Leaves dimorphic, submerged and floating; seeds smooth; male spathe with 10–30 male flowers           3. O. cordata

4b.     Leaves not dimorphic, emersed; seeds densely hairy; male spathe with 47–60 male flowers      4. O. emersa

1. Ottelia alismoides (Linnaeus) Persoon, Syn. Pl. 1: 400. 1805.

龙舌草  long she cao

Statiotes alismoides Linnaeus, Sp. Pl. 1: 535. 1753; Damasonium indicum Willdenow; Ottelia alismoides f. oryzetorum Komorov; O. condorensis Gagnepain; O. dioecia S. Z. Yan; O. indica Planchon; O. japonica Miquel.

Petiole varying greatly in length according to depth of water; leaf blade wholly submerged, varying greatly in shape and size, usually broadly ovate, ovate-elliptic, nearly orbicular, cordate, or sometimes lanceolate, ca. 20 × 18 cm or more, membranous. Flowers bisexual or plants occasionally dioecious-polygamous. Spathe 2.5–4 × 1.5–2.5 cm, 2- or 3-lobed at apex, with 3–6 longitudinal wings. Flowers solitary, sessile. Petals white, slightly purple, or bluish. Stamens 3–9(–12); filaments glandular hairy; anthers narrowly oblong, 3–4 mm. Ovary nearly globose, with 3–9(or 10) carpels; styles 6–10, deeply 2-lobed. Fruit 2–5 × 0.8–1.8 cm. Seeds fusiform, 1–2 mm, densely hairy. Fl. and fr. Apr–Oct. 2n=44.

In still or running water. Anhui, Fujian, Guangdong, Guangxi, Guizhou, NW Hainan, Hebei, Heilongjiang, Henan, Hubei, Hunan, Jiangsu, Jiangxi, Sichuan, Taiwan, Yunnan, Zhejiang [Cambodia, India, Indonesia, Japan including Ryukyu Islands, Korea, Laos, Malaysia, Myanmar, Nepal, Thailand, Vietnam; Africa, Australia, introduced into North America].

2. Ottelia sinensis (H. Léveillé & Vaniot) H. Léveillé ex Dandy, J. Bot. 72: 137. 1934.

贵州水车前  gui zhou shui che qian

Boottia sinensis H. Léveillé & Vaniot, Repert. Spec. Nov. Regni Veg. 5: 10. 1908; Ottelia balansae (Gagnepain) Dandy; O. demersa H. Li & C. X. You.

Leaves wholly submerged, translucent, young leaves linear or lanceolate, mature ones usually oblong or ovate, 20–40 × 6–9 cm, base truncate, rounded, or cordate, apex acute or rounded; petiole ca. 20 cm. Spathe elliptic, 3–6 × ca. 1.5 cm, with many longitudinal ribs and often with wings on lateral sides, with 3–11 flowers. Flowers bisexual. Sepals green. Petals white with yellow base, obtriangular or obovate, 2–3 × ca. 2.5 cm. Stamens 3; filaments 4–5 mm; anthers elliptic, 4–5 mm; glands 3. Ovary trianglular-cylindrical, with 3 carpels; styles 3, hairy; stigmas 6, hairy. Fruit narrowly elliptical, 5–9 cm × ca. 8 mm. Seeds cylindrical to fusiform, ca. 3 mm. Fl. and fr. Jun–Nov.

Ponds, rivers, lakes. Guangxi, Guizhou, Yunnan [Vietnam].

3. Ottelia cordata (Wallich) Dandy, J. Bot. 72: 137. 1934.

水菜花  shui cai hua

Boottia cordata Wallich, Pl. Asiat. Rar. 1: 52. 1830.

Leaves dimorphic; submerged leaves narrowly elliptic to ligulate, 30–60 × 4.5–10 cm; floating leaves broadly lanceolate or oblong-ovate, 10–20 × 4–10 cm, base cordate, apex acute to acuminate; petioles 30–120 cm. Flowers unisexual. Spathe oblong-ovate, 3.5–8 × 1.5 –2 cm, with 6 longitudinal ribs, bifid at apex. Male spathe with 10–30 male flowers. Sepals yellowish. Petals white, obovate, 2.5–4.5 cm. Stamens 12; filaments densely hairy; anthers ca. 6 mm; staminodes 3; reduced pistil 1; glands 3. Female spathe with only 1 female flower; perianths similar with male ones. Ovary oblong, with 9–15 carpels; styles 9–18, papillate, bifid at apex; staminodes 3–8; glands 3. Fruit oblong, 4–4.5 × 1.6–2 cm. Seeds fusiform, ca. 1.5 mm, smooth. Fl. May. 2n = 22.

Ponds, channels. Hainan [Cambodia, Myanmar, Thailand].

4. Ottelia emersa Z. C. Zhao & R. L. Luo, J. Wuhan Bot. Res. 5: 339. 1987.

出水水菜花  chu shui shui cai hua

Leaves emersed; petiole 45–90 cm; leaf blade narrowly cordate, 9–20 × 4.5–14 cm, leathery, base cordate, apex obtuse. Flowers unisexual. Spathe 5–7.5 × 3–3.5 cm, with 3 longitudinal ribs. Male spathe with 47–60 male flowers. Sepals greenish. Petals white with yellow base, obovate, 4–5.5 cm. Stamens 12; filaments upper densely hairy; anthers 4–9 mm; staminodes 3; reduced pistil 1. Female spathe with only 1 female flower; perianth larger than male ones; ovary ovoid, with 14–16 carpels; styles 14–18, bifid and hairy at apex; staminodes 6–9. Fruit oblong, 4.5–7 × 3–5 cm. Seeds fusiform, ca. 1.6 mm, densely hairy. Fl. May. 2n = 22.

* Ponds. Guangxi (Guixian).

This species differs from Ottelia cordata, by leaves emersed and not dimorphic, male flowers in each spathe with up to 47–60 flowers, and with densely hairy seeds.

5. Ottelia acuminata (Gagnepain) Dandy, J. Bot. 72: 137. 1934.

海菜花  hai cai hua

Leaves wholly submerged; petioles varying greatly in length according to depth of water; leaf blades varying greatly in shape and size, linear to broadly cordate, base cordate to attenuate, margin entire, undulate, or serrulate, apex obtuse. Flowers unisexual. Spathe with 2–6 longitudinal ribs. Male spathe with 40–190 male flowers. Sepals green. Petals white with yellow base, obcordate or obovate, 1–3.5 cm; stamens 9–12; filaments hairy; anthers ovoid-elliptic; staminodes 3. Female spathe with 2–9 female flowers; perianth similar to male ones; ovary triangular-cylindric with 3 carpels; styles 3, deeply bifid; staminodes 3. Fruit triangular-cylindrical to fusiform, ca. 8 cm. Seeds narowly elliptical, with or without hairs. Fl. May–Oct. 2n = 22. Fl.

* Lakes, ponds, channels, paddy fields. Guangdong, Guangxi, Guizhou, Hainan, Sichuan, Yunnan.

1a.. Male spathe with 60–190 flowers; female spathe with 8 or 9 flowers ............  5d. var. jingxiensis

1b.. Male spathe with 40–50 flowers; female spathe with 2 or 3 flowers.

2a.. Male spathe without veins, with bulbs within ...........................................  5c. var. linanensis

2b.. Male spathe with several veins, without bulbs within.

3a.. Fruit triangular-conical; leaves not ligulate ........................................  5a. var. acuminata

3b.. Fruit slightly curved, fusiform; leaves ligulate ..........................................  5b. var. crispa

5a. Ottelia acuminata var. acuminata

海菜花(原变种)  hai cai hua (yuan bian zhong)

Boottia acuminata Gagnepain, Bull. Soc. Bot. France 54: 538. 1907; B. yunnanensis Gagnepain; Ottelia acuminata (Gagnepain) Dandy var. tonhaiensis H. Li; O. cavaleriei Dandy; O. yunnanensis (Gagnepaiin) Dandy.

Leaves linear to broadly cordate, base usually cordate, margin entire or minutely serrulate. Spathe with 2–6 ribs. Male spathe with 40–50 male flowers. Female spathe with 2 or 3 female flowers; male flowers with filiform staminodes. Fruit triangular-conical; seeds without hairs.

* Lakes, ponds, channels, paddy fields. Guangdong, Guangxi, Guizhou, Hainan, Sichuan, Yunnan.

5b. Ottelia acuminata var. crispa (Handel-Mazzetti) H. Li, Acta Phytotax. Sin. 19(1): 36. 1981.

波叶海菜花  bo ye hai cai hua

Boottia crispa Handel-Mazzetti, Anz. Akad. Wiss. Wien, Math.-Naturwiss. Kl. 62: 253. 1925; Ottelia crispa (Handel-Mazzetti) Dandy

Leaves ligulate, base attenuate to subcordate, margin undulate. Fruit slightly curved, fusiform.

* Lakes. Yunnan (Luguhu).

5c. Ottelia acuminata var. lunanensis H. Li, Acta Phytotax. Sin. 19(1): 38. 1981.

路南海菜花  lu nan hai cai hua

Male spathe small, without ribs, with bulbs within; male flowers with minute, obcordate or ligulate staminodes.

* Lakes. Yunnan (Lunan).

5d. Ottelia acuminata var. jingxiensis H. Q. Wang & X. Z. Sun, J. Wuhan Bot. Res. 10(1): 12. 1992.

靖西海菜花  jing xi hai cai hua

Male spathe with 60–190 male flowers, female spathe with 8 or 9 female flowers; staminodes of male flowers bifid at apex. Seeds sparsely hairy.

* Rivers, streams. Guangxi (Jingxi).

2. HYDROCHARIS Linnaeus, Sp. Pl. 2: 1036. 1753.

水鳖属  shui bie shu

Herbs, floating. Stems short, stoloniferous. Leaves basal, floating or submerged, rarely emerged, petiolate and stipulate; blade ovate, orbicular, or reniform, entire, with more than 5 curved veins, sometimes with a central pad of spongy tissue on abaxial surface of floating blade. Plants monoecious; flowers unisexual; spathes 1- or 2-valved, male spathes pedunculate, 1–6-flowered, female spathes sessile, 1-flowered. Sepals greenish white. Petals white or yellowish, much larger than sepals. Stamens 6–12; anthers 2-thecous. Ovary elliptic; ovules numerous; styles 6, bifid. Fruit with 6 ribs, irregularly dehiscent at apex. Seeds ellipsoid.

About three species: Africa, Asia, Australia, Europe, and North America; one species in China.

1. Hydrocharis dubia (Blume) Backer, Handb. Fl. Java. 1: 64. 1925.

水鳖  shui bie

Pontederia dubia Blume, Enum. Pl. Java 1: 33. 1827; Hydrocharis asiatica Miquel; H. morsus-ranae Linnaeus; H. morsus-ranae var. asiatica (Miquel) Makino.

Leaves floating or sometimes emerged; blade cordate or orbicular, 4.5–5 × 5–5.5 cm, 5–7-veined, base cordate, apex rounded. Male flowers 5 or 6 in spathe; peduncles 0.5–3.5 cm; pedicels 5–6.5 cm; sepals ca. 6 × 3 mm; petals yellow, ca. 1.3 × 1.7 cm; stamens 12, inner 3 stamens staminodial; anthers 1–1.5 mm; staminodes hairy at base and papillose at apex. Female flowers larger than male flowers; sepals ca. 1.1 cm × 4 mm; petals white, yellow at base, ca. 1.5 × 1.8 cm; staminodes 6; glands 3, reniform; styles ca. 4 mm, with dense glandular hairs. Fruit berrylike, spherical to obovoid, 8–10 mm, ca. 7 mm in diam. Seeds gradually acute toward apex. Fl. and fr. Aug–Oct. 2n = 16.

In still water. Anhui, Fujian, Guangdong, Guangxi, NE Hainan, Hebei, Heilongjiang, Henan, Hubei, Hunan, Jiangsu, Jiangxi, Jilin, Liaoning, Shaanxi, Shandong, Sichuan, Taiwan, Yunnan, Zhejiang [India, Indonesia, Japan including Ryukyu Islands, Myanmar, New Guinea, Philippines; N Australia].

3. ENHALUS L. C. Richard, Mem. Cl. Sci. Math. Inst. Natl. France 12(2): 64. 181.

海菖蒲属  hai chang pu shu

Herbs, submerged marine; rhizome robust, with persistent fibrous remains of leaf sheaths. Leaves 2–6, narrowly linear or ribbon-shaped, sheathing at base, with many parallel veins, unequal at apex. Plants dioecious; flowers unisexual. Male inflorescence shortly pedunculate, enclosed by 2 spathal bracts; flowers numerous, minute, shortly pedicellate, breaking off just before anthesis, floating on surface of water at maturity; tepals reflexed; stamens 3; anthers subsessile, latrorsely dehiscent; pollen grains very large; female inflorescence 1-flowered, with a long peduncle, enclosed by 2 overlapping, scarcely fused, strongly keeled spathal bracts; sepals narrowly elliptic; petals linear; carpels 6, fused; styles 6, bifid. Fruit irregularly dehiscent. Seeds few.

One species: widely distributed along the coasts of the Indian Ocean and west Pacific Ocean; also in China.

1. Enhalus acoroides (Linnaeus f.) Richard ex Steudel, Nomencl. Bot. 1: 554. 1840.

 海菖蒲  hai chang pu

Statiotes acoroides Linnaeus f., Suppl. 268. 1781; Enhalus koenigii Richard.

Roots robust, 10–20 cm long, 3–5 mm in diam. Leaves 0.3–1.5 m × 1–2 cm, veins 13–19, margin entire, apex obtuse. Peduncle of male inflorescences ca. 5 cm, bracts sessile, slightly keeled, midvein hairy; male flowers with pedicels; sepals white, oblong, ca. 2 mm; petals white, larger than sepals; stamens white, 1.5–2 mm. Peduncle of female flower to 50 cm, coiled and contracted after anthesis; bracts 4–6 × 1–2 cm, midvein keeled, apparently hairy; sepals reddish; petals white, strap-shaped, strongly folded, 4–5 cm × 3–4 mm, papillose; ovary ovoid, with long hairs. Fruit ovoid, 5–7 cm. Seeds angular, 1–1.5 cm in diam. Fl. May.

Submerged in shallow sea water along coast. Hainan [Throughout coastline of SE Asia].

4. THALASSIA Banks & K. D. König, Ann. Bot. 2: 96. 1805 (‘1806’).

泰来藻属  tai lai zao shu

Herbs, submerged marine. Rhizome elongated, creeping, with scales and extended internodes, giving rise to erect, short, leafy shoots. Leaves usually 2–6, distichous, ribbonlike or slightly falcate, veins 9–15, parallel, connected by cross veins, sheathed at base. Inflorescences pedunculate, 1-flowered; spathes 2, fused; flowers unisexual, plants dioecious. Male flowers pedicellate; perianth segments 3; stamens 3–12; anthers subsessile, 2–4-thecous, latrorsely dehiscent; pollen grains spherical, stuck together into moniliform chains. Female flowers subsessile; ovary 1-loculed; styles 6, each with 2 filiform stigmas. Fruit spherical or elliptic, split open at top by stellate dehiscence of fleshy pericarp into a number of irregular valves. Seeds numerous.

Two species: Indian and W Pacific Ocean, Caribbean Sea, Gulf of Mexico; one species in China.

1. Thalassia hemprichii (Ehrenberg) Ascherson, Petermanns Geogr. Mitt. 17: 242. 1871.

泰来藻  tai lai zao

Schizotheca hemprichii Ehrenberg, Abh. Acad. Berl. Wiss. 1: 429. 1832.

Rhizomes tetrete, with persistent leaf sheaths. Leaves curved, 6–12(–40) cm × 4–8 mm. Peduncle of male inflorescence 2–3 cm, female inflorescence without peduncle; spathe linear. Male flower on a pedicel 2–3 cm; perianth segments elliptic, petaloid; anthers oblong. Female flower with ovary of 6 carpels; stigmatic branches 1–1.5 cm. Fruit greenish, 2–2.5 × 1.8–3.2 cm.

Submerged in shallow sea water along coast. Hainan, Taiwan [India, Japan (Ryukyus) Malaysia, Myanmar, Thailand].

5. BLYXA Noronha ex Thouars, Gen. Nova Madag. 4. 1806.

水筛属  shui shai shu

Herbs, submerged freshwater. Stems short or elongated, erect or stoloniferous. Leaves basal or spirally arranged along stem, sessile, lanceolate or linear, with prominent midvein and several lateral veins, sheathed at base, minutely serrulate along margin. Spathe tubular, sessile or pedunculate, bifid at apex, with longitudinal veins, 1-flowered or sometimes several flowered. Flowers bisexual or unisexual. Sepals 3, persistent, green, linear or lanceolate. Petals 3, white, longer than sepals. Stamens 3–9; filaments slender; anthers 4-thecous; Pistils 3; ovary linear, attenuate into a long, filiform beak; styles 3; ovules numerous. Fruit linear to terete, long, narrow. Seeds numerous, oblong-fusiform, smooth or with spines, sometimes with a filiform projection from each end.

About 11 species: tropical and subtropical regions; five species in China.

1a.     Stems elongate; leaves cauline.

2a.    Spathe sessile; anthers 1.8–2.5 mm; styles 3–4 mm; seeds narrowly elliptic ...  1. B. japonica

2b.    Spathe shortly pedunculate; anthers 3.5–5 mm; styles 5–6 mm; seeds ovoid  2.. B. leiosperma

1b.     Stems much shortened, or absent; leaves basal.

3a.    Flowers unisexual; stamens 9 .....................................................................  5. B. octandra

3b.    Flowers bisexual; stamens 3.

4a.     Seeds with a filiform projection from each end, and with prominent acute spines on surface      4. B. echinosperma

4b.     Seeds without a projection, and with broad, short, obtuse tubercules or ridges  3. B. aubertii

1. Blyxa japonica (Miquel) Maximowicz ex Ascherson & Gürke in Engler & Prantl, Pflanzenfam. 2(1): 253. 1889.

水筛  shui shai

Hydrilla japonica Miquel, Ann. Mus. Bot. Lugduno-Batavi 2: 271. 1866; Blyxa laevissima Hayata; Ottelia japonica Miquel.

Stems elongated, 10–20 cm tall, branched. Leaves cauline, lanceolate, 3–6 cm × 1–3 mm, veins 3, apex acuminate. Spathes sessile, green, 1–3 cm × 1–3 mm. Flowers bisexual. Sepals green with purple midvein, linear-lanceolate, 2–4 × 0.5–1 mm. Petals 6–10 × 0.5–1 mm. Stamens 3; filaments 1–3 mm, smooth; anthers 1.8–2.5 mm. Ovary conical; styles 3–4 mm. Fruit 1–2.5 cm. Seeds 30–60, narrowly elliptic, smooth. Fl. and fr. May–Oct. 2n = 72.

Paddy fields, ponds, channels. Anhui, Fujian, Guangdong, Guangxi, Guizhou, Hainan, Hubei, Hunan, Jiangsu, Jiangxi, Liaoning, Sichuan, Taiwan, Zhejiang [Bangladesh, India, Japan, Korea, Malaysia, Myanmar, Nepal, Thailand; Europe].

2. Blyxa leiosperma Koidzumi, Bot. Mag. (Tokyo) 31: 257. 1917.

光滑水筛  guang hua shui shai

Stems elongated, 2–6 cm tall, branched from base. Leaves cauline, lanceolate, 6–9 cm × ca. 2.5 mm, veins 3, apex acuminate. Spathes green, 2.5–3 cm × ca. 2 mm, with peduncle 0.2–2.2 cm. Flowers bisexual. Sepals yellowish green, linear-lanceolate, 4–5 × ca. 0.5 mm; petals 9–10 × ca. 1 mm; stamens 3; filaments 3–5 mm; anthers 3.5–5 mm. Ovary conical; styles 5–6 mm. Fruit 2.5–3 cm. Seeds 40–60, ovoid, smooth. Fl. and fr. May–Sep. 2n = 72.

Paddy fields. Anhui, Fujian, Guangdong, Hainan, Jiangxi, Zhejiang [Japan].

3. Blyxa aubertii Richard, Mem. Cl. Sci. Math. Phys. Inst. France, [Mem. Inst. Paris] 12(2): 19. 1812.

无尾水筛  wu wei shui shai

Blyxa ecaudata Hayata.

Stems shortened. Leaves all in basal rosette, linear, 5–17(–60) cm × 3–(12) mm, veins 5–9, apex acuminate. Spathes green, 3–5 cm × ca. 2 mm, with peduncle 2.7–8 cm. Flowers bisexual. Sepals greenish purple, linear-lanceolate, 5–7 × ca. 1 mm. Petals 9–17 × ca. 0.5 mm. Stamens 3; filaments 3–6 mm; anthers 1–1.8 mm. Ovary narrowly cylindrical, 2.5–4 cm; styles ca. 7 mm. Fruit (2–)4–6(–8) cm. Seeds 30–70, oblong-ovoid, 1.2–1.8 × ca. 0.6 mm, ca. 6–12-ribbed; ribs obscurely tuberculate or ridged. Fl. and fr. May–Sep. 2n = 16.

Paddy fields and channels. Fujian, Guangdong, Guangxi, Hainan, Hunan, Jiangxi, Sichuan, Taiwan, Yunnan, Zhejiang [Bangladesh, Bhutan, India, Japan (Ryukyus), Korea, Malaysia, Myanmar, Nepal, Sri Lanka, Thailand; Africa, Australia, introduced into North America].

4. Blyxa echinosperma (C. B. Clarke) J. D. Hooker, Fl. Brit. India 5: 661. 1888.

有尾水筛  you wei shui shai

Hydrotrophus echinospermus C. B. Clarke, J. Linn. Soc., Bot. 14: 8. 1873; Blyxa aubertii var. echinosperma (C. B. Clarke) Cook & Lüönd; B. bicaudata Nakai; B. ceratosperma Maximowicz ex Ascherson & Guerke; B. shimadai Hayata; B. somai Hayata.

Stems shortened. Leaves all in basal rosette, strap-shaped, 10–20(–40) cm × 4–7 mm, veins 7–9, apex acuminate. Spathes green, 2–5 cm × ca. 2 mm, with slender peduncle 2–12 cm, Flowers bisexual. Sepals green, linear, ca. 6 × 1 mm; petals 1–1.4 cm × 0.5–0.8 mm. Stamens 3, 4–6 mm. Ovary narrowly cylindrical, 3–7 cm; styles 0.6–1.5 cm. Fruit 4–7 cm. Seeds 30–50, fusiform or oblong-fusiform, 1.5–2 × ca. 0.8 mm, with filiform projections or ridges 2–12 mm from each end, and with prominently acute spines on surface. Fl. and fr. Jun–Oct. 2n = 42.

Paddy fields and channels. Anhui, Fujian, Guangdong, Guangxi, Guizhou, Hebei, Hunan, Jiangsu, Jiangxi, S Shaanxi, Sichuan, Taiwan, Zhejiang [Bangladesh, India, Indonesia, Japan, Korea, Malaysia, Myanmar, Nepal, Papua New Guinea, Philippines, Sri Lanka, Thailand, Vietnam; Australia].

5. Blyxa octandra (Roxburgh) Planchon ex Thwaites, Enum. Pl. Zeyl. 332. 1864.

八药水筛  ba yao shui shai

Vallisneria octandra Roxburgh, Pl. Coromandel 2: 34. 1802; Blyxa roxburghii Richard.

Stems shortened or absent. Leaves all in basal rosette, linear, 6–60 cm × 0.5–0.7 mm; veins faint, 20 or more, spiny toward apex. Spathes 6–10 cm, with a long peduncle 20–120 cm. Plants dioecious; flowers unisexual, one female or 5–10 male flowers in a spathe. Sepals reddish, linear, 9–10 × ca. 1.5 mm. Petals 2–2.5 cm or longer. Stamens 9; filaments 2–5 mm; anthers 1–2 mm. Ovary narrowly cylindrical, 6–9 cm, with a beak 8–10 cm; styles ca. 2 cm, hairy. Fruit 7.5–10 cm. Seeds numerous, oblong-elliptic, 1–2 × 0.5–1 mm, with up to 12 longitudianal ridges bearing 8 rows of ± blunt spines ca. 0.5 mm, without filiform projections. 2n=16, 32.

Guangdong, Guangxi (Fangchen), Sichuan, Yunnan [Bangladesh, India, New Guinea, Sri Lanka; Australia].

6. VALLISNERIA Linnaeus, Sp. Pl. 2: 1015.1753.

苦草属  ku cao shu

Herbs, submerged, stoloniferous, without erect stems. Leaves basal, sessile, linear or strap-shaped, veins 3–9, parallel, slightly sheathed at base, margin minutely serrulate or entire. Plants dioecious; flowers unisexual. Male flowers numerous, minute, shortly pedicellate, clustered together on a central column enclosed by a common spathe, each flower finally breaking free and floating on water surface; spathe ovate or broadly lanceolate, shortly pedunculate; sepals 3, convex, 2 larger than the third; petals 3 or 2, minute; stamens 1–3; female spathe tubular, bifid at apex, pedunculate; peduncles long, coiled after anthesis. Female flowers solitary in spathe; sepals 3; petals 3, minute. Ovary narrowly cylindrical or narrowly triangular-cylindrical; ovules numerous; styles 3, bifid. Fruit cylindrical or triangular-cylindrical. Seeds numerous, oblong or fusiform.

About eight species: tropical and subtropical; three species in China (one endemic).

1a.     Stamen 1; fruit cylindrical; veins without spines ...................................................  1. V. natans

1b.     Stamens 2; fruit triangular-cylindrical; midveins with minute spines.

2a.    Seeds 2–5-winged ....................................................................................  2. V. spinulosa

2b.    Seeds without wings .........................................................................  3. V. denseserrulata

1. Vallisneria natans (Loureiro) H. Hara, J. Jap. Bot. 49: 136. 1974.

苦草  ku cao

Physkium natans Loureiro, Fl. Cochinch. 663. 1790; Vallisneria asiatica Miki; V. asiatica var. higoensis Miki, V. gigantea Graebner; V. gigantea var. higoensis (Miki) Kitamura; V. higoensis (Miki) Ohwi; V. natans var. higoensis (Miki) H. Hara; V. spiraloides Roxburgh.

Rhizome tuberous; stolons ca. 2 mm in diam., usually smooth. Leaves 0.2–2 m × 0.5–2 cm, veins 5–9, margin entire or inconspicuously serrulate, apex obtuse. Male spathe ovate-conical, 1.5–2 cm × 5–10 mm, with more than 200 male flowers; sepals strongly convex; stamens 1, filaments sometimes 2-lobed at apex, with hairs at base. Female spathe 1.5–2 cm; peduncle 30–50 cm or longer, slender. Sepals greenish purple, 2–4 × ca. 3 mm, apex obtuse; petals white, minute; staminodes 3. Fruit cylindrical, 5–30 cm × ca. 5 mm. Seeds narrowly obovoid, glandular hairy. 2n = 20.

Rivers, streams, ponds, lakes. Anhui, Fujian, Guangdong, Guangxi, Guizhou, Hebei, Henan, Hubei, Hunan, Jiangsu, Jiangxi, Jilin, Liaoning, Shaanxi, Shandong, Sichuan, Taiwan, Yunnan, Zhejiang [India, Japan including Ryukyus, Malaysia, Nepal; SW Asia, Australia].

2. Vallisneria spinulosa S. Z. Yan, J. Sci. Med. Jinan Univ. 2: 161. 1982.

刺苦草  ci ku cao

Rhizome tuberous; stolons with minute spines. Leaves 20–50(–200) cm × 4–10 mm, midveins prominent, with 1 row of minute spines, margin serrulate, apex obtuse or slightly acute. Male spathe conical, 1–1.5 cm × 5–8 mm, with more than 300 male flowers; sepals convex; petals 2, connected at base of filaments; stamens 2, filaments without hairs. Female spathe 1–2 cm, with very long slender peduncle; sepals ca. 4 × 2 mm, apex obtuse; petals minute; staminodes 3. Fruit triangular-cylindrical, 8–20 cm × 4–7 mm, with spines on angles. Seeds obovoid, 2–5-winged. Fl. and fr. Aug–Oct. 2n = 20.

* Ponds, lakes. Guangxi, Hubei, Hunan, Jiangsu.

3. Vallisneria denseserrulata (Makino) Makino, J. Jap. Bot. 2: 19. 1921.

密刺苦草  mi ci ku cao

Vallisneria spiralis Linnaeus var. denseserrulata Makino, Bot. Mag. (Tokyo) 28: 27. 1914.

Rhizome erect, 1–6 cm long, 4–6 mm in diam.; stolons with minute spines. Leaves 20–70 cm × 6–12 mm, veins 3, midvein with minute spines, margin densely serrulate, apex obtuse or acute. Male spathe triangular, 1–1.5 cm × ca. 6 mm, many flowered; sepals reflexed; stamens 2. Female spathe 1.5–2 cm, with slender and very long peduncle; sepals ca. 3 × 2 mm, apex acute. Fruit triangular-cylindrical. Seeds not winged. Fl. and fr. Sep–Oct. 2n = 20.

Streams, lakes. Anhui, Guangdong, Guangxi. Hubei, Liaoning, Zhejiang [Japan].

7. NECHAMANDRA Planchon, Ann. Sci. Nat. 11: 78. 1849.

虾子草属  xia zi cao shu

Herbs, submerged. Stems elongated, slender, much branched. Leaves alternate but usually opposite at base, densely crowded toward ends of stems, linear, lacking a prominent midvein, parallel veins present, slightly sheathing at base, margin minutely serrulate with teeth. Plants dioecious; flowers unisexual. Male inflorescence pedunculate, many flowered; spathe ovate, membranous, bifid at apex; male flowers minute; sepals 3, petaloid, white, ovate; petals 3, small, nearly equal to sepals; stamens 2 or 3, opposite to sepals; filaments slender, very short. Female spathe oblong, 1-flowered; female flowers similar to male ones; ovary oblong, elongated into a beak at apex; styles 3. Fruit ovoid-oblong or linear. Seeds numerous, oblong, minute.

Only one species: Asia, including China.

1. Nechamandra alternifolia (Roxburgh ex R. Wight) Thwaites, Enum. Pl. Zeyl. 332. 1864.

虾子草  xia zi cao

Vallisneria alternifolia Roxburgh ex R. Wight, Hooker's Bot. Mag. Misc. 2: 344. 1831; Lagarosiphon alternifolia (Roxburgh ex R.Wight) Druce; Nechamandra roxburghii Planchon.

Leaves 2–7 cm × 1–1.5 mm, midvein slightly distinct, apex acute. Male inflorescence with 60–100 flowers; peduncle translucent; spathe translucent, ca. 5 × 4 mm; male flowers with slender pedicel ca. 0.6 mm; sepals transparent; filaments ca. 0.3 mm. Female spathe tubular, ca. 5 mm, sessile; sepals 0.5–1 × 0.4–0.7 mm; ovary 5–10 mm, flattened, margin on each side serrulate; styles retuse at apex, densely papillate. Fl. and fr. Sep–Oct. 2n = 14.

Ponds, lakes, slow-moving rivers and channels. Guangdong, Guangxi [Bangladesh, India, Nepal, Sri Lanka, Vietnam].

8. HYDRILLA L. C. Richard, Mém. Cl. Sci. Math. Inst. Natl. France 1811(2): 9, 61. 1814.

黑藻属  hei zao shu

Herbs, submerged. Stems elongated, branched. Leaves verticillate or lowermost opposite, sessile, linear to narrowly elliptic, margin serrate with 2 small, fringed nodal scales. Plants dioecious or monoecious; flowers unisexual, axillary. Male spathe subsessile, membranous, subglobose, with apical knob and corona of setae, 1-flowered; male flowers shortly pedicellate, free from spathe on water surface at anthesis; sepals 3, ovate or obovate, convex; petals 3, narrower than sepals; stamens 3. Female spathe tubular, sessile, bifid at apex, 1-flowered; sepals and petals similar to male ones; ovary cylindric, attenuate into a filiform beak; styles (2 or)3; ovules few. Fruit cylindric or linear.

One species and variety: temperate to tropical; one species and variety in China.

1. Hydrilla verticillata (Linnaeus f.) Royle, Ill. Bot. Himal. Mts. 1: t. 376. 1839.

黑藻  hei zao

Leaves in whorls of 3–8, linear or narrowly strap-shaped, 0.7–1.7 cm × 1–4 mm, midvein distinct, margin conspicuously denticulate, apex acute. Male spathe green; sepals white, ca. 2.3 × 0.7 mm; petals reflexed, white, or reddish, ca. 2 × 0.5 mm; female spathe green; flowers similar to male ones. Fruit with 2–9 spinelike projections or smooth and without projection. Seeds (1 or)2–6. Fl. and fr. May–Oct. 2n = 16, 24.

Ponds, running water. Anhui, Fujian, Guangdong, Guangxi, Guizhou, Hainan, Hebei, Henan, Heilongjiang, Hubei, Hunan, Jiangsu, Jiangxi, Liaoning, Shaanxi, Shandong, Sichuan, Taiwan,  Xizang, Yunnan, Zhejiang [Bangladesh, Bhutan, India, Indonesia, Japan, Malaysia, Myanmar, Nepal, Pakistan, Philippines, Russia, Sri Lanka, Thailand; Australia: Europe, introduced into North America].

1a.. Fruit with 2–9 spine-like projections; seeds 2–6 ............................................  1a. var. verticillata

1b.. Fruit smooth, without spine-like projections; seeds 1–3 ..................................  1b. var. roxburghii

1a. Hydrilla verticillata var. verticillata

黑藻 (原变种)  hei zao (yuan bian zhong)

Serpicula verticillata Linnaeus f., Suppl. 416. 1781; Elodea verticillata (Linnaeus f.) F. Mueller; Hydrilla dentata Caspary.

Leaves 0.7–1.7 cm × 1–1.8 mm. Fruit with 2–9 spinelike projections; seeds 2–6. 2n = 16.

Ponds, running water. Anhui, Fujian, Guangdong, Guangxi, Guizhou, Hainan, Hebei, Heilongjiang, Henan, Hubei, Hunan, Jiangsu, Jiangxi, Liaoning, Shaanxi, Shandong, Sichuan, Taiwan, Xizang, Yunnan, Zhejiang [Indonesia, Japan, Malaysia, Philippines; Australia, Europe].

1b. Hydrilla verticillata var. roxburghii Caspary, Jahrb. Wiss. Bot. 1: 494. 1858.

罗氏轮叶黑藻  luo shi lun ye hei zao

Leaves 0.7–1.3 cm × 3–4 mm. Fruit smooth, without spine-like projections; seeds 1–3, usually without embryo. 2n = 24.

Ponds, running water. Anhui, Fujian, Guangdong, Guangxi, Guizhou, Hainan, Hebei, Heilongjiang, Henan, Hubei, Hunan, Jiangsu, Jiangxi, Shaanxi, Shandong, Sichuan, Taiwan, Yunnan, Zhejiang [Japan, Malaysia, Philippines; Australia, Europe].

9. HALOPHILA Thouars, Gen. Nov. Madag. 2: 2. 1808.

喜盐草属  xi yan cao shu

Herbs, submerged marine. Stems slender, easily breaking, creeping, branched, rooting at nodes, with 2 scales at each node. Leaves usually opposite or binate, usually petiolate, margin entire or serrulate. Plants dioecious or monoecious; flowers unisexual; spathes 2-valved, sessile, usually 1-flowered. Male flowers pedicellate; perianth segments 3; stamens 3, alternate with perianth segments, filament absent; anthers 2–4-thecous, extrorse; pollen moniliform. Female flowers sessile or subsessile; ovary with a apical beak; beak expanded at apex into 3 minute perianth lobes; ovules 2 to numerous; styles (2 or)3–5, threadlike. Fruit with beak at apex; pericarp membranous. Seeds few to many, globose or subglobose.

About nine species: along the coasts of W Indian and S Pacific Oceans; four species in China.

1a.     Lateral shoots 1–1.5 cm, each with 6–10 leaves; leaves narrowly elliptic to lanceolate, without cross veins     4. H. beccarii

1b.     Lateral shoots shorter than 1 cm, each with only one pair of leaves; leaves ovate to elliptic, with 3–25 pairs of cross veins.

2a.    Leaves 0.5–1.2 cm, cross veins in 3–8 pairs and diverging from midvein at an angle of 70–90º     3. H. minor

2b.    Leaves 1–4 cm, cross veins in 6–25 pairs and diverging from midvein at an angle of 45–60º.

3a.     Leaves 1–4 cm, entire and smooth, cross veins in 12–25 pairs ......................  1. H. ovalis

3b.     Leaves 1–2.2 cm, margin finely serrulate, pubescent on both surfaces, cross veins in 6–9 pairs            2. H. decipiens

1. Halophila ovalis (R. Brown) J. D. Hooker, Pl. Tasm. 2: 45. 1858.

喜盐草  xi yan cao

Caulina ovalis R. Brown, Prodr. 1: 339. 1810; Halophila euphlebia Makino; H. hawaiiana Doty & B. C. Strong.

Creeping stems elongated, internodes 1–5 cm; scales orbicular to obovate, keeled, 4–5.5 × 3–3.5 mm, membranous, transparent; lateral shoots scarcely developed. Leaves 1-paired at each node; petiole 1–4.5 cm; leaf blade transparent, oblong-elliptic or ovate, 1–4 × 0.5–2 cm, entire, with 12–16(–25) pairs of cross veins running from midvein to intramarginal veins and diverging from midvein at an angle of 45–60°. Male spathes broadly lanceolate, ca. 4 mm; perianth segments elliptic, ca. 4 mm. Female spathes broadly lanceolate, with a neck at apex, inner one enclosed within outer one; ovary slightly triangular; styles long, slender; stigmas 3, 2–3 cm. Fruit ellipsoid-globular, 3–4 mm in diam.; beak 4–5 mm. Seeds numerous, ca. 1 mm. Fl. Nov–Dec. 2n = 18.

Submerged in shallow seas. Guangdong, Hainan, Taiwan [India, Indonesia (Java), Japan, Malaysia, Myanmar, Philippines, Thailand; from the Red Sea to W Pacific Ocean].

2. Halophila decipiens Ostenfeld, Bot. Tidsskr. 24: 260. 1902.

毛叶喜盐草  mao ye xi yan cao

Creeping stems with internodes 1–3.2 cm; scales membranous, transparent. Petiole 1–2 cm; leaf blade oblong-elliptic, 10–22 × 3–7 mm, midvein prominent, with one diverging pair of intramarginal veins at base, with cross veins 6–9 pairs. Plants monoecious. Spathes ovate, ca. 3-3.5 mm, with abaxial hairs. Ovary ca. 1.4 mm; styles short, ca. 2 mm, stigmas 3. Fruit globose, ca. 2.5 × 1.5 mm. Seeds 10–15(–30), globose, 0.4–0.6 mm.

Submerged in shallow seas. Taiwan [tropical seas of Indian Ocean, Pacific Ocean, and Caribbean].

3. Halophila minor (Zollinger) Hartog, Fl. Males., ser. 1, 5(4): 410. 1957.

小喜盐草  xiao xi yan cao

Lemnopsis minor Zollinger, Syst. Verz. 1: 75. 1854; Halophila lemnopsis Miquel.

Creeping stems with internodes 1–3 cm; scales transparent, nearly orbicular or elliptic, 2–4 mm, membranous; lateral shoots scarcely developed. Leaves 1-paired at each node; petiole 0.5–3.5 cm; leaf blade transparent, narrowly elliptic or ovate, 5–12 × 3–5 mm, entire, with 3–8 pairs of cross veins running from midvein to intramarginal veins and diverging from midvein at an angle of 70–90°. Male spathes ovate or nearly orbicular, ca. 3 mm, keeled; perianth segments transparent, ca. 2.5 mm. Female spathes lanceolate, with a neck at apex, inner one enclosed within outer one; ovary ovoid, 1–2 mm; styles elongated; stigmas 3, 0.6–1.7 cm. Fruit ovoid or globular, 2–4 mm; beak 2–6 mm. Seeds ca. 20, ca. 0.5 mm in diam.

Submerged in shallow seas. Guangdong, Hainan, Taiwan [India, Indonesia (Java), Japan, Malaysia, Phillipines].

4. Halophila beccarii Ascherson, Nuovo Giorn. Bot. Ital. 3: 302. 1871.

贝克喜盐草  bei ke xi yan cao

Creeping stems with internodes 1–2 cm; scales membranous, transparent, outer one 2–3 × 2–2.5 mm, inner one 4–6 × 4–4.5 mm; lateral shoots erect, 1–1.5 cm. Leaves 6–10 at apex of each lateral shoot; petiole 1–2 cm; leaf blade narrowly elliptic or lanceolate, 6–11 × 1–2 mm, midvein prominent, with one diverging pair of intramarginal veins at base, without cross veins, sheath to 3–4 mm, margin entire. Plants dioecious. Spathes oblong or lanceolate, ca. 2.5 mm, keeled. Ovary ca. 1 mm; styles elongated; stigmas 2 or 3. Fruit ovoid, 0.5–1.5 mm, beaked. Seeds 2–4, small.

Submerged in shallow seas. Guangdong, Hainan, Taiwan [Malaysia, Myanmar, Philippines, Sri Lanka; SE Asia].

10. EGERIA Planchon, Ann. Sci. Nat., Bot, sér. 3, 11: 79. 1849.

水蕴草属 shui yun cao shu

Herbs, perennial, freshwater. Rhizomes and stolons absent. Stems erect, rooted in substrate, branched or unbranched, elongate. Leaves cauline, in whorls of 5 or more, submersed, sessile; blade linear, base sloping to stem, apex obtuse; midvein without rows of lacunae along sides, blade uniform in color throughout; abaxial surface without prickles or aerenchyma; intravaginal squamules entire. Inflorescences 1-flowered, sessile; spathes not winged. Flowers unisexual, staminate and pistillate on different plants, projected to surface by slender, elongate floral tube base, pedicellate; petals white. Staminate flowers: filaments distinct, anthers linear; pollen in monads. Pistillate flowers; ovary 1-locular; styles 3, not 2-fid. Fruit ovoid smooth, dehiscing irregularly. Seeds fusiform, mucilaginous.

Three species: South America, introduced into North America, Eurasia, Africa, and Australia; one species introduced into China.

1. Egeria densa Planchon, Ann. Sci. Nat., Bot., sér. 3, 11: 80. 1849.

水蕴草 shui yun cao

Stems 1–3 mm diam. Leaves whorled, recurved, 10–40 × 1.5–4.5 mm, margin minutely serrate. Staminate spathes 2–4-flowered, 7.5–12 mm; pedicel to 8 cm. 2n=46.

Known from a cultivated fish pond. Guangdong. This species is known to spread and become invasive in mild climates.