fu ping ke

Li Heng; Elias Landolt

Herbs, mostly perennial, minute, aquatic, floating or submersed, reduced to small green bodies called fronds corresponding partly to leaf and partly to stem. Roots absent or 1–21, filiform, arising from lower side of frond; root hairs absent. Fronds 1–many cohering together, circular or oblong to lanceolate and flat or convex on lower side (gibbous), or globular to ovoid, 0.4–1.5 cm, with or without veins; daughter fronds successively formed from 1 basal cavity or 2 basal pouches detaching or remaining attached for many weeks. Node (point of origin of veins, roots and daughter fronds) situated c. 1/3 from base towards apex. Turions (in some species) formed under unfavourable conditions, frondlike, but smaller, compact, sinking to bottom. Flowers (interpreted as inflorescences by some authors) rare in most species, 1 (or 2), emerging from one of the pouches or from a cavity near median line on upper surface; sepals and petals absent; stamens 1 or 2; ovary 1, bottle-shaped, 1–7-ovuled, tapering into short style; stigma 1, funnel-shaped. Fruit indehiscent, opening by bursting.

Five genera and 38 species: worldwide in aquatic ecosystems; four genera and eight species in China.

Lemnaceae species grow often together with other species of the same family, sometimes also with water ferns. They are usually gregarious and multiply rapidly (up to doubling within 24 hours). The fronds of all species are used as high quality feed for domestic animals, fish and fowl.

1. SPIRODELA Schleiden, Linnaea 13: 391. 1839

zi ping shu

Fronds free floating, 1–10 cohering together, usually asymmetrical, flat or sometimes convex (gibbous) on lower side, shiny green above, often red beneath, with 2 lateral pouches at base, reproducing daughter fronds and (rarely) 1 flower, surrounded at base by small membraneous scale covering point of attachment of the roots; veins (5–)7–21, leaving from node towards apex, sometimes visible on upper surface. Pigment cells present (visible in dead fronds as brown dots). Roots 5–21, surrounded at base by a tubular sheath, enclosed at tip by a rounded to pointed cap. Daughter fronds connected to mother frond by thin white stipe. Flower surrounded by small utricular, membranous scale with narrow opening at top; stamens 2, 4-locular. Seeds 1–3, longitudinally ribbed.

Two species: one species worldwide, one species only in Central and South America; one species in China.

1. Spirodela polyrrhiza (Linnaeus) Schleiden, Linnaea 13: 392. 1839

zi ping

Lemna polyrhiza Linnaeus, Sp. Pl.: 970. 1753

Fronds obovate to circular, 3–10 mm, 1–1.5 times as long as wide, flat or (rarely) gibbous, sometimes with indistinct papillae on upper surface along veins. Roots (5–)7–21, 1 (or 2) perforating scale, 0.5–3 cm. Turions sometimes present, without roots, circular to reniform, 1–2 mm, brownish to olive. Flower with 1 or 2 ovules. Fruit laterally winged towards top; seed with 12–20 ribs. Fl. (very rare) Jun–Sep. 2n = 30, 32, 38, 40*, 50, 80.

Ponds, lakesides, rice fields, pools, ditches; lacking in regions with cool summers. 0–2900 m. Anhui, Fujian, Guangdong, Guangxi, Guizhou, Hebei, Heilongjiang, Henan, Hubei, Hunan, Jiangsu, Jiangxi, Jilin, Liaoning, Quinghai, Shaanxi, Shandong, Shanxi, Sichuan, Taiwan, Yunnan, Zhejiang [all continents].

Gibbous fronds of S. polyrrhiza are sometimes named var. masonii Daubs. This variant occurs rarely throughout the whole distribution and is of no systematic value.

S. polyrrhiza is used as Chinese medicinal herb for diuretics, for subsides of swellings and for reducing perspiration.

2. LANDOLTIA Les & Crawford, Novon 9: 532. 1999

see note at top

Fronds free floating, 1–10 cohering together, usually asymetrical, flat or gibbous, shiny green above, often red beneath, with 2 lateral pouches at base, reproducing daughter fronds and (rarely) 1 flower, surrounded at base by small membraneous scale covering point of attachment of the roots; veins (3–)5–7, leaving from node towards apex, often visible on upper surface. Pigment cells present (visible in dead fronds as brown dots). Roots (1–)2–7(–12), surrounded at base by a tubular sheath, enclosed at tip by a rounded or pointed cap. Daughter fronds connected to mother frond by thin white stipe. Flower surrounded by small utricular, membraneous scale with a slit on one side (rarely on 2 sides); stamens 2, 4-locular. Seeds 1(–2), longitudinally ribbed.

One species: originally probably distributed only in SE Asia and Australia, now introduced in subtropical and tropical zones worldwide; one species in China.

1. Landoltia punctata (G. Meyer) Les & Crawford, Novon 9: 532. 1999

see note at top

Lemna punctata G. Meyer, Prim. Fl. Esseq.: 262. 1818; Spirodela punctata (G. Meyer) C.H. Thompson; Spirodela oligorrhiza (Kurz) Hegelm.

Fronds obovate to elliptic, 1.5–8 mm, 1.5–3 times as long as wide, flat or gibbous, mostly with papillae on upper surface along midvein. Roots (1–)2–7(–12), all perforating scale, 0.5–7 cm. No distinct turions present. Flower with 1 or 2 ovules. Fruit laterally winged towards top; seed with 10–15 distinct ribs. Fl. (rare) Jun–Sep. 2n = 40*, 46, 50.

Ponds, lakesides, pools, ditches; in regions with mild winters and not very hot summers. 0–2400 m. Fujian, Henan, Hubei, Sichuan, Taiwan, Xizang, Yunnan, Zhejiang [India, Indonesia, Japan, Malaysia, Philippines, Thailand, Vietnam; Africa, Australia, North America, Pacific Islands, South America].

M.G. Liu and K.M. Xie described 1983 a new species of Spirodela from Sichuan under the name S. sichuanensis. The species has been distinguished from S. punctata (now Landoltia punctata) mainly by the form of the utricular scale surroundig the flower: the scale has 2 lateral slits in S. sichuanensis and one lateral slit in L. punctata. However, the 2 slits can rarely also be observed in other places of the distribution area of L. punctata. Due to the rarity of flowering, the frequency of this character is not known. All the vegetative characters of S. sichuanensis stay within the morphologiocal variation of L. punctata.

3. LEMNA Linnaeus, Sp. Pl. 2: 970. 1753

fu ping shu

Fronds free floating on the water surface or submersed, 1 to many cohering together, symmetrical or asymmetrical, flat or sometimes convex beneath (gibbous), green above, sometimes red beneath, with 2 lateral pouches at base, reproducing daughter fronds and (rarely in most species) 1 flower, not surrounded by a scale at base; veins 1–5(–7), leaving from node towards apex. Pigment cells absent. Root 1, sometimes dropped off or lacking (L. trisulca), surrounded at base by a short tubular sheath and enclosed at tip by a cap. Daughter fronds connected to mother frond by a thin white stipe or a green stalk (L. trisulca). Flower surrounded by small utricular, membranous scale; stamens 2, 4-locular. Seeds 1–5, longitudinally ribbed.

Thirteen species: nearly cosmopolitan; five species in China.

1. Lemna trisulca Linnaeus, Sp. Pl. 2: 970. 1753.

pin zao

Fronds (except when flowering or fruiting) submersed, 3–50, coherent in groups and often forming branched chains, transparent green, sometimes purplish, narrowed at base into a 2–20 mm long green stalk, 3–15 mm (without stalk), 2–3.5 times as long as wide, narrowly ovate to elliptic, flat, without papillae on upper surface; margins denticulate distally; veins (1 or) 3, central vein reaching nearly apex, lateral veins only about halfway between node and apex. Root 0.5–2.5 cm, often lacking; sheath not winged; tip mostly pointed. Turions absent. Flowering and fruiting fronds free floating on water surface, 1–5, coherent, 3–5 mm. Flower with 1 ovule; utricular scale with narrow opening at top. Fruit laterally winged towards top; seed with 12–18 distinct ribs. Fl. (rare) May–Sep. 2n = 20, 40, 42, 60, 63, 80.

Lakesides, spring pools, ponds; in regions with cool temperate climate. 0–3000 m. Anhui, Hebei, Heilongjiang, Hubei, Jiangsu, Nei Mongol, Shaanxi, Shanxi, Sichuan, Taiwan, Xinjiang, Yunnan, Zhejiang [Afghanistan, India, Japan, New Guinea, Kasakhstan, Kyrgyzstan, Pakistan, Philippines, Russia; all continents except South America].

2. Lemna turionifera Landolt, Aquatic Botany 1: 355. 1975.

name

Fronds free floating on water surface, 1–8, coherent in small groups, shiny green, sometimes with reddish spots on upper surface and red coloured on lower surface (always deeper red on lower surface than on upper), rounded at base, without a green stack (but with thin white stipe connecting fronds), 1.5–4 mm, 1–1.5 times as long as wide, obovate, flat, with distinct papillae on midline of upper surface; margins entire; veins 3, reaching nearly apex, greatest distance between lateral veins near or distal to middle. Root 0.5–15 cm; sheath not winged, tip rounded (to pointed). Turions often present, 0.5–1.5 mm, olive–brown, rootless. Flower with 1 ovule; utricular scale with narrow opening at top. Fruit not winged towards top; seed with 30–60 indistinct ribs. Fl. (rare) Jun–Sep. 2n = 40, 42, 50, 80.

Lakesides, spring pools, ponds, slowly flowing streems; in regions with continental cool temperate climate. 0–3000 m. Anhui, Hebei, Heilongjiang, Nei Mongol [Korea, N Japan, Russia; North America, Asia, Europe (introduced)].

3. Lemna japonica Landolt, Veröff. Geobot. Inst. ETH, Stiftg. Rübel, 70: 23. 1980.

name

Lemna minor auct mult. non Linnaeus

Fronds free floating on water surface, 1–8, coherent in small groups, shiny green, sometimes reddish or red on lower surface (always deeper red on lower surface than on upper), rounded at base, without a green stalk (but with thin white stipe connecting fronds), 2–6(–7) mm, 1.3–1.8 times as long as wide, obovate to elliptic, flat or sligtly convex on lower side, with mostly distinct papillae on upper surface near apex and above node and indistinct ones along the midline; margins entire; veins 3(–5), reaching nearly apex, greatest distance between lateral veins near or proximal to middle. Root 0.5–15(–18) cm; sheath not winged, tip rounded (to pointed). Turions absent. Flower with 1 ovule; utricular scale with narrow opening at top. Fruit not known. Fl. (very rare) Jul–Oct. 2n = 40*, 50, 63.

Lakesides, pools, ponds, ditches; in regions with moderate to warm temperate climate. 0–2900 m. Hebei, Heilongjiang, Henan, Hubei, Jiangsu, Nei Mongol, Shaanxi, Shandong, Shanxi, Yunnan, Zheijiang [Korea, Japan].

L. japonica probably originated from hybridization between L. minor and L. turionifera.

M.G. Liu & C.H. You described 1983 Lemna leibonensis from S. Sichuan which is most probably identical with L. japonica. It is distinguished by larger fronds, conspicious veins and pointed root caps. These characters occur also within L. japonica..

4. Lemna minor Linnaeus, Sp. Pl. 2: 970. 1753.

fu ping

Fronds free floating on water surface, 1–8, coherent in small groups, shiny green, sometimes reddish on upper surface, scarcely reddish on lower surface (always deeper red on upper surface than on lower), rounded at base, without a green stalk (but with thin white stipe connecting fronds), 2–6(–10) mm, 1.3–2 times as long as wide, obovate to elliptic, flat, with mostly distinct papillae on upper surface near apex and above node; margins entire; veins 3(–5), reaching nearly apex, greatest distance between lateral veins near or proximal to middle. Root 0.5–15 cm; sheath not winged, tip mostly rounded. Turions absent. Flower with 1 ovule; utricular scale with narrow opening at top. Fruit winged laterally towards top; seed with 10–16 distinct ribs. Fl. (rare) May–Sep. 2n = 20, 40, 42, 50, 63, 126.

Lakesides, pools, ponds, ditches, slow flowing streams in regions with suboceanic cool to moderate temperate climate. (0–) 2000–3000 m. W. Xizang [Afghanistan, N India, Kazakhstan, Nepal, N Pakistan, W Russia, Turkmenistan; Africa, SW Asia, Japan (introduced), Europe, North America, Australia (introduced), New Zealand (introduced)].

5. Lemna aequinoctialis Welwitsch, Apont. Conselh. Ultramar. 55: 578. 1859.

xi mai fu ping

Lemna paucicostata Hegelmaier; Lemna perpusilla auct. mult. non Torrey; Lemna trinervis (Austin) Small

Fronds free floating on water surface, 1–8 coherent in small groups, shiny bright green, without reddish colour, rounded at base, without a green stalk (but with thin white stipe connecting fronds), 1.5–4(–6.5) mm, 1–3 times as long as wide, obovate to lanceolate, flat, with mostly very distinct papillae on upper surface near apex and above node; margins entire; veins 3, reaching nearly apex, greatest distance between lateral veins nearly or proximal to middle. Root 0.5–3 cm; sheath winged towards the base, tip mostly pointed. Turions absent. Flower with 1 ovule; utricular scale with slit on one side. Fruit not winged; seed with 8–24 distinct longitudinal ribs. Fl. (frequent) all seasons. 2n = 20, 40*, 42, 50*, 60, 70, 80, 84.

Lakesides, pools, ponds, rice fields, ditches; in regions with warm temperate to tropical climate. 0–2800 m. Anhui, Fujian, Guangdong, Guizhou, Hebei, Henan, Hubei, Jiangsu, Jiangxi, Liaoning, Quinghai, Shaanxi, Shandong, Shanxi, Taiwan, Yunnan, Zhejiang [Afghanistan, Bangladesh, Bhutan, Cambodia, India, Indonesia, Japan, Korea, Laos, Malaysia, Myanmar, Nepal, New Guinea, Pakistan, Philippines, Singapore, Sri Lanka, Thailand, Vietnam; all continents].

Plants with large thin fronds with conspicuous veins and without distinct papillae are often called L.trinervis. This character combination represents just a modification occurring throughout the range of L. aequinoctialis.

6. Lemna minuta Kunth in A. von Humboldt & al., Nov. Gen. Sp. 1: 372. 1816.

name

Lemna minima Phil.; Lemna minuscula Herter

Fronds free floating on water surface, 1–8, coherent in small groups, bright green, without reddish colour, rounded at base, without a green stalk (but with thin white stipe connecting fronds), 0.8–4 mm, 1–2 times as long as wide, obovate, flat to thickish (but not convex on lower side), with or without indistinct papillae on midline of upper surface; margin entire; vein 1, not longer than 2/3 of the distance between node and apex. Root 0.2–1.5 cm; sheath not winged, tip rounded to pointed. Turions absent. Flower with 1 ovule; utricular scale with slit on one side. Fruit not winged; seed with 12–15 distinct ribbs. Fl. (very rare) May–Sep. 2n = 36, 40, 42.

Lakesides, spring pools, ponds, ditches; in regions with suboceanic moderate to warm temperate climate. 0-->3000m. Not known from China but likely to be introduced [C Japan (introduced); America, Europe (introduced)].

4. WOLFFIA Horkel ex Schleiden, Beitr. Bot.: 233. 1844.

wu gen ping shu

Fronds free floating on or below the water surface, 1 or 2 cohering together, symmetrical, globular, ovoid or boat-shaped, green above, green to transparent beneath, never reddish, with 1 basal cavity reproducing daughter fronds, not surrounded by a scale at base; veins absent. Pigment cells (in our species) absent in vegetative cells. Roots absent. Daughter fronds connected to mother frond by a very short stipe (not visible). Flower emerging from a cavity near median line of upper surface, not surrounded by a scale; stamens 1, 2-locular. Seed 1, nearly smooth.

Eleven species: nearly cosmopolitan; one species in China.

1. Wolffia globosa (Roxburgh) Hartog & Plas, Blumea 18: 367. 1970.

wu gen ping

Lemna globosa Roxburgh, Fl. Ind. 3: 565. 1832;Wolffia arrhiza auct. mult. non (Linnaeus) Horkel

Fronds free floating on or just below water surface, green on upper surface, transparent green below, ovoid, 0.4–0.8 mm, 1.3–2 times as long as wide, 1–1.5 times as deep as wide, rounded or sligtly pointed at apex; papillae absent. Turions sometimes present, 0.3–0.5 mm, whitish green, globular. Fl. (very rare) Jun–Sep. 2n = 16, 23, 30, 40*, 46, 50, 60.