Najas (PDF)

Fl. China 23: 91–95. 2010. 

1. NAJAS Linnaeus, Sp. Pl. 2: 1015. 1753. 

茨藻属 ci zao shu 

Herbs, annual, small, submerged in fresh or brackish water. Stem slender, fragile, much branched, rooting at base and lowermost 

nodes. Leaves subopposite or pseudowhorled, sessile, linear, small, 1-veined, sheathing at base, margin spinulose-toothed; 

sheaths variously shaped, often auriculate. Plants monoecious or dioecious; flowers minute, unisexual, solitary or few in leaf axil. 

Male flowers spatulate or rarely not spatulate; perianth (often named “involucre” or “envelope”) 2-lipped, membranous, closely 

applied to anther; stamen 1, anther subsessile, 1–4-thecous, dehiscing at apex. Female flowers sessile; spathe absent or rarely present; 

perianth persistent. Fruit an elliptic-oblong achene; pericarp thin, membranous, indehiscent, persistent. Seeds without endosperm; 

testa hard, brittle, pitted; embryo straight. 

About 40 species: cosmopolitan; eleven species (one endemic) in China. 

One of the Fl. China editorial committee, Wu Zhengyi, prefers to keep the Najadaceae separate because of its distinct morphology in having 

superior ovaries and nuclear endosperms. 

1a. Plants dioecious; stems and abaxial surface of leaves usually spiny; areoles on seeds irregularly arranged ................. 1. N. marina 

1b. Plants monoecious; stems and abaxial surface of leaves usually not spiny; areoles on seeds longitudinally arranged. 

2a. Anthers 1-thecous. 

3a. Seeds with many transversely elongated ladderlike pits; areoles fusiform; fruit narrowed and slightly 

curved at apex ........................................................................................................................................................ 2. N. minor 

3b. Seeds with many longitudinally elongated pits; areoles rectangular or polygonal; fruit usually straight. 

4a. Auricles broadly triangular; leaves in pseudowhorls of 3 ..................................................................... 5. N. browniana 

4b. Auricles orbicular or obcordate; leaves in pseudowhorls of 5. 

5a. Male spathe present .......................................................................................................................... 3. N. gracillima 

5b. Male spathe absent ................................................................................................................ 4. N. pseudogracillima 

2b. Anthers 4(or rarely 2)-thecous. 

6a. Auricles broadly triangular to linear. 

7a. Male flowers without spathe .................................................................................................................. 10. N. graminea 

7b. Male flowers with spathe ............................................................................................................ 11. N. pseudograminea 

6b. Auricles rounded to obcordate. 

8a. Fruit semilunate; female flowers with spathe ................................................................................... 6. N. ancistrocarpa 

8b. Fruit elliptic; female flowers without spathe. 

9a. Areoles hexangular, transversely elongated, arranged in ladderlike manner ................................. 7. N. oguraensis 

9b. Areoles rectangular or irregularly arranged. 

10a. Auricles orbicular; testa with apparently raised cell walls ....................................................... 8. N. chinensis 

10b. Auricles obcordate; testa without raised cell walls ................................................................... 9. N. foveolata 

1. Najas marina Linnaeus, Sp. Pl. 2: 1015. 1753. 

大茨藻 da ci zao 

Stems 30–100 cm or more tall, 1–4.5 mm in diam., mostly 

armed with spines, spines sometimes absent except apically. 

Leaves 1.5–3 cm × 2–3.5 mm, fleshy, abaxial side of midvein 

usually with spines; sheath ca. 3 mm, entire or serrulate with 1– 

3 spine cells on upper side without auricle, leaf acute at apex, 

with 2–10 conspicuous teeth on each side of margin; teeth 1–2 

mm. Plants dioecious; flowers yellowish green. Male flowers 

ca. 5 × 2 mm; spathe with a short neck; anther 4-thecous. Female 

flowers 2–4.5 mm; style ca. 1 mm; stigmas 2- or 3-lobed. 

Fruit elliptic to obovoid-elliptic, 4–6 × 3–4 mm. Seeds ovoid; 

testa pitted; areoles polygonal, irregularly arranged. Fl. and fr. 

Sep–Nov. 2n = 12*, 24, 48, 60*. 

Ponds, lakes, slow-moving rivers; below 2700 m. Anhui, Guangdong, 

Guangxi, Hebei, Heilongjiang, Henan, Hubei, Hunan, Jiangsu, 

Jiangxi, Jilin, Liaoning, Nei Mongol, Shandong, Shanxi, Taiwan, Xinjiang, 

Yunnan, Zhejiang [India, Japan, Kazakhstan, Korea, Kyrgyzstan, 

Malaysia, Mongolia, Myanmar, Pakistan, Russia, Sri Lanka, 

Tajikistan, Turkmenistan, Uzbekistan, Vietnam; Africa, SW Asia, Aus- 

tralia, Europe, North and South America]. 

1a. Stems without spines except at apex; 

abaxial side of leaf midvein without 

spines ................................................. 1c. var. brachycarpa 

1b. Stems with spines; abaxial side of leaf 

midvein with spines. 

2a. Seeds 2.5–4 mm; style and stigma 

0.2–1.4 mm; anther 1–3.3 mm ..... 1d. var. intermedia 

2b. Seeds 4–6 mm; style and stigma 

2–3 mm; anther ca. 4 mm. 

3a. Margins of leaves with 4–10 

conspicuous teeth; stems 

with spines ................................. 1a. var. marina 

3b. Margins of leaves with 2 or 

4 teeth; stems with only 1 

or 2 spines under nodes ... 1b. var. grossidentata 

1a. Najas marina var. marina 

大茨藻(原变种) da ci zao (yuan bian zhong) 

Ittnera major (Allioni) C. C. Gmelin; Najas major Allioni; 

N. major var. angustifolia A. Braun; N. marina var. angustifolia

(A. Braun) K. Schumann. 

Stems mostly armed with spines. Leaves with 4–10 

conspicuous teeth on margin, abaxial side of midvein with 

spines ca. 2 mm. Style and stigma 2–3 mm; anthers 3.8–4 mm. 

Seeds 4.5–5.7 × 2–2.8 mm. 

Ponds, lakes, slow-moving rivers; below 2700 m. Anhui, Guangdong, 

Guangxi, Hebei, Heilongjiang, Henan, Hubei, Hunan, Jiangsu, 

Jiangxi, Jilin, Liaoning, Nei Mongol, Shandong, Shanxi, Taiwan, Xinjiang, 

Yunnan, Zhejiang [India, Japan, Korea, Malaysia, Russia, Tajikistan; 

Africa, Australia, Europe, North America]. 

1b. Najas marina var. grossidentata Rendle, Trans. Linn. Soc. 

London, Bot. 5: 396. 1899. 

粗齿大茨藻 cu chi da ci zao 

Stems stout, with only 1 or 2 spines under nodes. Margins 

of leaves with 2 or 4 teeth, abaxial side of midvein with sparse 

spines. Style and stigma 2–3 mm; anthers 3.8–4 mm. Seeds 4– 

4.5 × 2.2–2.4 mm. 

Ponds, lakes. Heilongjiang, Jilin, Liaoning [Korea]. 

1c. Najas marina var. brachycarpa Trautvetter, Bull. Soc. 

Imp. Naturalistes Moscou 40(3): 97. 1867. 

短果茨藻 duan guo ci zao 

Najas intramongolica Y. C. Ma; N. marina subsp. brachycarpa 

(Trautvetter) Tzvelev. 

Stems slightly slender, with spines only at apex. Leaves 

smaller, abaxial side of midvein without spines. Style and stigma 

0.2–1.4 mm; anthers 1–3.3 mm. Seeds 2.2–2.5 × 1.5–1.8 

mm. 

Ponds. Nei Mongol, Xinjiang [C Asia]. 

1d. Najas marina var. intermedia (Gorski) Ascherson, Fl. 

Brandenburg 1: 670. 1864. 

小果大茨藻 xiao guo da ci zao 

Najas intermedia Gorski in Eichwald, Naturhist. Skizze, 

126. 1830; N. marina subsp. intermedia (Gorski) Casper. 

Stems only slightly spiny. Leaves with 4–8 conspicuous 

teeth on margin, abaxial side of midvein with spines. Style and 

stigma 0.2–1.4 mm; anthers 1–3.3 mm. Seeds 2.5–4 × 1.2–2 

mm. 

Ponds. Yunnan [cold to warm-temperate areas from Europe to C 

Asia, extending to a few subtropical parts of Asia]. 

2. Najas minor Allioni, Auct. Syn. Meth. Stirp. Horti Regii 

Taur. 3. 1773. 

小茨藻 xiao ci zao 

Caulinia minor (Allioni) Cosson & Germain; Fluvialis 

minor (Allioni) Persoon; Ittnera minor (Allioni) C. C. Gmelin; 

Najas moshanensis N. Z. Wang. 

Stems 4–25 cm tall, 0.5–1 mm in diam. Leaves recurved, 

1–3 cm × 0.5–1 mm; sheath ca. 2 mm; auricles truncate to 

rounded, with more than 10 teeth on upper and outer sides of 

leaf margin, each side serrulate with 6–12 teeth, apex acumi- 

nate. Plants monoecious; flowers yellowish green. Male flowers 

elliptic, 0.5–1.5 mm; spathe with a short neck, with brownish 

spine cells at apex; anther 1-thecous. Female flowers ca. 2 mm; 

style 1–1.7 mm; stigmas 2-lobed. Fruit linear-ellipsoid, 2–3 × 

ca. 0.5 mm, narrowed and slightly curved at apex. Seeds 

narrowly ellipsoid, with many rows of transversely elongated 

ladderlike pits; areoles fusiform. Fl. and fr. Jun–Oct. 2n = 12*, 

24*, 36, 46, 56. 

Ponds, lakes, paddy fields and channels; below 2700 m. Anhui, 

Fujian, Guangdong, Guangxi, Hainan, Hebei, Heilongjiang, Henan, Hubei, 

Hunan, Jiangsu, Jiangxi, Jilin, Liaoning, Nei Mongol, Shandong, 

Taiwan, Xinjiang, Yunnan, Zhejiang [Afghanistan, India, Indonesia 

(Java), Japan (including Ryukyu Islands), Kazakhstan, Korea, Nepal, 

Pakistan, Philippines, Sri Lanka, Tajikistan, Thailand, Uzbekistan, Vietnam; 

Africa, SW Asia, Europe; introduced in North America]. 

3. Najas gracillima (A. Braun ex Engelmann) Magnus, Beitr. 

Kenntn. Najas, 23. 1870. 

纤细茨藻 xian xi ci zao 

Najas indica (Willdenow) Chamisso var. gracillima A. 

Braun ex Engelmann in A. Gray, Manual, ed. 5, 681. 1867; N. 

japonica Nakai. 

Stems 8–20 cm tall, 0.3–0.5 mm in diam. Leaves often in 

pseudowhorls of 5, ca. 2 cm × 0.3–0.5 mm; sheath 1–2 mm; 

auricles orbicular to slightly obcordate, short, minutely serrulate 

with 6 or 7 teeth, upper margin on each side minutely serrulate 

with 7–11 teeth. Plants monoecious; flowers 1–4 per axil, male 

flowers in upper axils and female ones throughout. Male flowers 

elliptic, 1–1.5 mm; spathe with a short neck, with brownish 

spine cells at apex; anther 1-thecous. Female flowers conspicuous, 

2–3 mm; style 1–2 mm; stigmas 2-lobed. Fruit linear-ellipsoid, 

2–3 × ca. 0.5 mm. Seeds narrowly ellipsoid, with more 

than 20 rows of pits; areoles oblong, longitudinally elongated. 

Fl. and fr. Jun–Aug. 2n = 12, 24. 

Paddy fields, shallow water of ponds and channels; below 1800 

m. Fujian, Guangxi, Guizhou, Hainan, Hebei, Hubei, Jiangxi, Jilin, 

Liaoning, Nei Mongol, Taiwan, Yunnan, Zhejiang [Japan; North 

America]. 

Najas gracillima is most similar to N. minor, especially in vegetative 

condition. However, N. gracillima can be separated from N. 

minor by its fruit often straight and the areoles of its seeds longer than 

broad. 

4. Najas pseudogracillima Triest, Mém. Acad. Roy. Sci. 

Outre-Mer, Cl. Sci. Nat. Méd., Collect. 8vo. 22: 98. 1988. 

拟纤细茨藻 ni xian xi ci zao 

Stems ca. 10 cm tall, ca. 0.3 mm in diam. Leaves often in 

pseudowhorls of 5, 9–11 × ca. 0.3 mm; sheath 1–2 mm; auricles 

orbicular to slightly obcordate, short, minutely serrulate with 3– 

5 teeth, upper margin on each side minutely serrulate with 6–10 

teeth. Plants monoecious; flowers 1–3 per axil, male flowers in 

upper axils and female ones below. Male flowers elliptic, 0.6– 

0.8 mm; spathe absent; anther 1-thecous. Female flowers inconspicuous, 

ca. 1 mm; style ca. 1 mm; stigmas 2- or 3-lobed. Fruit 

1.6–2 × ca. 0.5 mm. Seeds elliptic-oblong, with more than 25 

rows of pits; areoles oblong, longitudinally elongated; cell walls

not raised. Fl. and fr. Jul–Nov. 

● Known only from ponds on Chung Chi Campus, Hong Kong. 

Najas pseudogracillima is most similar to N. gracillima, especially 

in vegetative condition. It differs by having male flowers without a 

spathe, whereas N. gracillima has male flowers with a spathe. 

5. Najas browniana Rendle, Trans. Linn. Soc. London, Bot. 5: 

420. 1899. 

高雄茨藻 gao xiong ci zao 

Stems 20–30 cm tall, ca. 1 mm in diam. Leaves often in 

pseudowhorls of 3, linear, 1–2 cm × 0.5–1 mm; sheath shortly 

auriculate; auricles triangular, ca. 2 mm, minutely serrulate with 

several teeth on apex; leaf margin on each side minutely serrulate 

with 10–20 teeth. Plants monoecious; flowers solitary or 

2 or 3 together. Male flowers ca. 1 mm; spathe with a short 

neck, with brownish spine cells at apex; anther 1-thecous. Female 

flowers linear-ellipsoid, ca. 1 mm; style short; stigmas 2lobed. 

Fruit linear-ellipsoid, 1.5–1.7 mm. Seeds narrowly ellipsoid, 

with many rows of pits; areoles squarish to pentangular. 

Fl. and fr. Aug–Nov. 2n = 12*. 

Brackish water. Guangdong, Guangxi, Taiwan [India, Indonesia, 

New Guinea; Australia]. 

According to Triest (Mém. Acad. Roy. Sci. Outre-Mer, Cl. Sci. 

Nat. Méd., Collect. 8vo. 22: 118. 1988), Najas browniana is found only 

in Australia. 

6. Najas ancistrocarpa A. Braun ex Magnus, Beitr. Kenntn. 

Najas, 7. 1870. 

弯果茨藻 wan guo ci zao 

Caulinia ancistrocarpa (A. Braun ex Magnus) Nakai; 

Najas poyangensis S. F. Guan & Q. Lang. 

Stems 10–30 cm tall, 0.5–1 mm in diam. Leaves narrowly 

linear or linear, 1–2 cm × ca. 0.5 mm; sheath 1–1.5 mm; auricles 

rounded, minutely serrulate with 5–8 teeth on upper side; 

leaf margin minutely serrulate with 4–16 (or more) spiny teeth 

on each side. Plants monoecious; flowers solitary. Male flowers 

0.5–1.5 mm; spathe with a short neck, with 4 or 5 brownish 

spine cells at apex; anther 4-thecous. Female flowers recurved, 

with a spathe; neck of spathe with brownish spine cells at apex; 

style ca. 0.5 mm; stigmas 2-lobed. Fruit semilunate, 1–2 × ca. 

0.5 mm. Seeds curved, fusiform, with many rows of pits; areoles 

oblong. Fl. and fr. Jul–Oct. 2n = 12*, 24. 

Still water. Fujian, Hubei, Jiangxi, Taiwan, Zhejiang [Japan]. 

7. Najas oguraensis Miki, Bot. Mag. (Tokyo) 49: 775. 1935. 

澳古茨藻 ao gu ci zao 

Caulinia oguraensis (Miki) Nakai. 

Stems 20–30 cm tall, 1–2.5 mm in diam. Leaves narrowly 

linear to subulate, 1–2 cm × 1–3 mm, slightly curved; midvein 

sometimes with spines; sheath 3–5 mm; auricles orbicular to 

obcordate, short, minutely serrulate with several teeth at apex; 

leaf margin serrulate with 7–14 teeth on each side. Plants 

monoecious; flowers solitary, male flowers usually in upper 

axils, female ones throughout. Male flowers elliptic, ca. 1 mm; 

spathe with a neck, with several brownish spine cells at apex; 

anther 4-thecous. Female flowers ca. 3 mm; style ca. 0.5 mm; 

stigmas 2-lobed. Fruit narrowly ellipsoid, 3–4 × ca. 1 mm, 

narrowed and curved at apex. Seeds narrowly ellipsoid, with 

many rows of transversely elongated ladderlike pits; areoles 

hexangular. Fl. and fr. Jul–Nov. 2n = 24, 60*. 

Still water. Hubei, Jiangxi, Taiwan [India, Japan, Korea, Nepal, 

Pakistan]. 

8. Najas chinensis N. Z. Wang, J. Wuhan Bot. Res. 3: 32. 1985. 

东方茨藻 dong fang ci zao 

Najas orientalis Triest & Uotila. 

Stems 10–15 cm tall, 0.5–1 mm in diam. Leaves linear to 

narrowly lanceolate, 1–3 cm × 0.2–1 mm; sheath ca. 2 mm; 

auricles rounded, minutely serrulate with several teeth on each 

side; leaf margin minutely serrulate with 6–20 teeth on each 

side. Plants monoecious; flowers solitary or sometimes 2 together, 

male flowers in upper axils and female ones throughout. 

Male flowers elliptic, ca. 1 mm; spathe with a neck, with 

several brownish spine cells at apex; anther 4-thecous. Female 

flowers 2–2.5 mm; style ca. 1 mm; stigmas 2–4(or 5)-lobed. 

Fruit narrowly ellipsoid, 2–2.5 × ca. 0.5 mm. Seeds slightly 

reniform, with ca. 20 rows of pits; areoles regularly arranged, 

subsquare; cell walls apparently raised. Fl. and fr. May–Aug. 2n 

= 12*. 

Ponds, channels, paddy fields, slow-moving rivers; below 1800 m. 

Fujian, Guangdong, Guangxi, Hainan, Hubei, Jiangxi, Jilin, Liaoning, 

Taiwan, Yunnan, Zhejiang [Japan; Europe]. 

Najas chinensis is similar to N. foveolata but can be easily 

separated by its rounded sheath and apparently raised cell walls of the 

seed coat. 

9. Najas foveolata A. Braun ex Magnus, Beitr. Kenntn. Najas, 

7. 1870. 

多孔茨藻 duo kong ci zao 

Caulinia foveolata (A. Braun ex Magnus) Nakai. 

Stems 10–20 cm tall, 0.5–1 mm in diam. Leaves linear, 

slender, 2–2.5 cm × 0.2–0.5 mm; sheath 2–2.5 mm; auricles 

obcordate, minutely serrulate with 4–9 teeth at apex and outer 

side; leaf margin on each side minutely serrulate with 6–24 

teeth. Plants monoecious; flowers solitary, male flowers in 

upper axils and female flowers throughout. Male flowers elliptic, 

ca. 1 mm; spathe with a short neck, with several brownish 

spine cells at apex; anther 4-thecous. Female flowers ca. 2.5 

mm; style ca. 1 mm; stigmas 2-lobed, unequal. Fruit narrowly 

ellipsoid, ca. 1.5 × 0.5 mm. Seeds narrowly ellipsoid, with ca. 

20 rows of pits; areoles subsquarish to polygonal. Fl. and fr. 

Aug–Sep. 2n = 12*, 24, 36. 

Ponds. Anhui, Guangxi, Hubei, Taiwan, Zhejiang [India, ?Indonesia, 

Malaysia]. 

Previously, this species was known only in China from S 

Guangxi. 

10. Najas graminea Delile, Descr. Égypte, Hist. Nat. 2: 282.

1813. 

草茨藻 cao ci zao 

Stems 10–20 cm tall, 0.5–1 mm in diam. Leaves narrowly 

linear to linear, 1–2.5 cm × 0.4–1 mm; sheath 1.5–3 mm, deeply 

auriculate; auricles narrowly triangular or lanceolate, 1–2 mm, 

serrulate with several teeth on each side, apex acute; leaf 

margin minutely and densely serrulate with 30–50 inconspicuous 

teeth on each side, consisting of brownish spine cells only. 

Plants monoecious; flowers solitary, or sometimes 2 or 3 together. 

Male flowers usually more toward upper axils, ca. 1 

mm, elliptic; spathe absent; anther 4-thecous. Female flowers 

1.5–2 mm; style ca. 1 mm; stigmas 2–4-lobed. Fruit oblong, 

1.5–2 × ca. 0.8 mm. Seeds ellipsoid-oblong, with ca. 30 rows of 

pits; areoles hexangular and irregularly polygonal toward ends, 

or rectangular. Fl. and fr. Jun–Sep. 2n = 12*, 24, 36*, 48, 72. 

Ponds, paddy fields, usually in still or slow-moving water; below 

1800 m. Anhui, Fujian, Guangdong, Guangxi, Hainan, Hebei, Henan, 

Hubei, Jiangsu, Liaoning, Sichuan, Taiwan, Yunnan, Zhejiang [Afghanistan, 

Bangladesh, India, Indonesia, Japan (including Ryukyu Islands), 

Kazakhstan, Korea, Malaysia, Myanmar, Nepal, New Guinea, Pakistan, 

Philippines, Sri Lanka, Tajikistan, Thailand, Uzbekistan, Vietnam; 

Africa, SW Asia, Australia, Europe; introduced in North America]. 

1a. Fruit not curved; areoles hexangular 

to polygonal .......................................... 10a. var. graminea 

1b. Fruit curved toward apex; areoles 

oblong .................................................... 10b. var. recurvata 

10a. Najas graminea var. graminea 

草茨藻(原变种) cao ci zao (yuan bian zhong) 

Caulinia graminea (Delile) Tzvelev. 

Leaves ca. 1 mm wide; auricles narrowly triangular. Fruit 

usually straight. Seeds with hexangular or irregularly polygonal 

areoles. 

Ponds, paddy fields, usually in still or slow-moving water. Anhui, 

Fujian, Guangdong, Guangxi, Hainan, Hebei, Henan, Hubei, Jiangsu, 

Liaoning, Taiwan, Yunnan [India, ?Indonesia, Japan (including Ryukyu 

Islands), Korea, Malaysia, Myanmar, Philippines; Africa, Australia, 

Europe; introduced in North America]. 

10b. Najas graminea var. recurvata J. B. He, L. Y. Zhou & H. 

Q. Wang, Bull. Bot. Res., Harbin 8(3): 126. 1988. 

弯果草茨藻 wan guo cao ci zao 

Leaves less than 0.5 mm wide; auricles shortly lanceolate. 

Fruit recurved at apex. Seeds with apparently oblong areoles. 

● Paddy fields. Hubei, Zhejiang. 

11. Najas pseudograminea W. Koch, Ber. Schweiz. Bot. Ges. 

44: 339. 1935. 

拟草茨藻 ni cao ci zao 

Najas tenuifolia R. Brown subsp. pseudograminea (W. 

Koch) W. J. de Wilde. 

Stems ca. 10 cm tall, ca. 1 mm in diam. Leaves often in 

pseudowhorls of 3, 16–20 × 0.6–0.9 mm; sheath 1–2 mm; 

auricles linear, short, minutely serrulate with 3–9 teeth, upper 

margin on each side minutely serrulate with 30–50 teeth. Plants 

monoecious; flowers 1–3 per axil, male flowers in upper axils 

and female ones below. Male flowers elliptic, 1.4–2.3 mm; 

spathe with short neck; anther 4-thecous. Female flowers inconspicuous, 

ca. 1 mm; style ca. 1 mm; stigmas 2- or 3-lobed. Fruit 

1–1.3 × ca. 0.4 mm. Seeds elliptic-oblong, with more than 20 

rows of pits; areoles squarish to hexagonal or rectangular; cell 

walls not raised. Fl. and fr. Jul. 

Known in China only from ponds on Chung Chi Campus, Hong 

Kong [East Timor, Indonesia, Philippines, Thailand; Australia].

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