Hydrocharitaceae
Najas

Najas testui Rendle

First published in J. Bot. 75: 51 (1937)
This species is accepted
The native range of this species is Tropical Africa. It is a hydroannual and grows primarily in the seasonally dry tropical biome.

Descriptions

Najadaceae, L. Triest (Vrije Universiteit, Brussels). Flora of Tropical East Africa. 1989

Morphology General Habit
Stems unarmed, ± 0.5 mm. in diameter, often plumose above because of the closely packed leaves.
Morphology Leaves
Leaves (6.5-)11.8-32 mm. long, flat, acute, linear-lanceolate (0.26-)0.42-0.72(-1.1) mm. wide including teeth on both sides, (0.24-0.53(-0.87) mm. wide excluding teeth); margin on each side minutely serrulate with inconspicuous spiny teeth, mainly consisting of the brownish spine-cell or serrulate with 7-30 conspicuous spiny teeth on broad triangular excrescences; teeth (0.05-)0.09-0.14 mm. long, the ratio of teeth-length to leaf-width being 0.13-0.3(-0.5); midrib without spiny teeth; septa absent or clearly visible; fibres absent or present on margin and/or near midrib; sheath (1.3-)1.9-2.4(-2.9), (including auricle and spine-cells) × (1.37-)2.6(-3.22) mm. (ratio = 0.8-1.6), truncate to auriculate, the auricle 0.24-0.96 mm. long (including spine-cells) and 0.2-1 mm. wide (ratio = 0.75-1.74), serrulate or lacerate with 2-8 spine-cells on each side; apex of the auricle rather obtuse.
Morphology Reproductive morphology Flowers
Male and ♀ flowers generally on different branches, solitary or several together, each at the very base of a (sometimes very short) axillary shoot. Male flower (1.2-)1.9-2.5 (including spathe-neck) × 0.4-1 mm., the neck of the spathe ± 0.6 mm., tapering at the top, bearing brownish spine-cells on the apex; inner envelope protruding 0.16-0.32 mm. above the anther; anther 1-2.4 × 0.36-1 mm., tetrasporangiate. Female flower enclosed in a spathe, (1.1-)1.5-3 (including spathe-neck) × 0.4-0.6 mm., the neck of the spathe about halfway along the style, bearing no brownish spine-cells on the apex; ovary 0.5-1(-1.77) × (0.3-)0.6 mm.; style and stigma 0.8-1.3 mm.; stigma 2-lobed.
sex Male
Male flower (1.2-)1.9-2.5 (including spathe-neck) × 0.4-1 mm., the neck of the spathe ± 0.6 mm., tapering at the top, bearing brownish spine-cells on the apex; inner envelope protruding 0.16-0.32 mm. above the anther; anther 1-2.4 × 0.36-1 mm., tetrasporangiate.
sex Female
Female flower enclosed in a spathe, (1.1-)1.5-3 (including spathe-neck) × 0.4-0.6 mm., the neck of the spathe about halfway along the style, bearing no brownish spine-cells on the apex; ovary 0.5-1(-1.77) × (0.3-)0.6 mm.; style and stigma 0.8-1.3 mm.; stigma 2-lobed.
Morphology Reproductive morphology Fruits
Fruit with persistent membranous pericarp and remnants of style and spathe.
Morphology Reproductive morphology Seeds
Seed elliptic-oblong to ovate, (1.85-)2-2.3(-2.6) × (0.4-)0.56-0.79 mm. (ratio = (2.3-)3.1-3.8); areoles 0.11-0.23 mm. long, irregularly arranged in longitudinal rows of 10-14(-23); cell-walls raised.
Habitat
Marshes and ponds, in and near rivers; 900-1700 m.
Distribution
K4 K5 K6 T7 U2 tropical Africa
[FTEA]

IUCN Red List of Threatened Species https://www.iucnredlist.org/species/185559/136681943

Conservation
LC - least concern
[IUCN]

Extinction risk predictions for the world's flowering plants to support their conservation (2024). Bachman, S.P., Brown, M.J.M., Leão, T.C.C., Lughadha, E.N., Walker, B.E. https://nph.onlinelibrary.wiley.com/doi/full/10.1111/nph.19592

Conservation
Predicted extinction risk: not threatened. Confidence: confident
[AERP]

J. R. Timberlake, E. S. Martins (2009). Flora Zambesiaca, Vol 12 (part 2). Royal Botanic Gardens, Kew

Type
Type Central African Republic, 120 km NE of Yalinga, 22.i.1922, Le Testu 3625 (BM holotype, K, L, P).
Morphology General Habit
Submerged, rooted aquatic herb, monoecious, slender
Morphology Stem
Stems unarmed, c.10 cm high, spreading and profusely branched above; branch thin
Morphology Leaves
Leaves (6.5)12–25(32) mm long, (0.26)0.42–0.72(1.1) mm wide including teeth (0.24–0.53(0.87) mm wide excluding teeth), linear-lanceolate, flat, acute; margins finely serrulate with 7–21 small teeth on each side; leaf teeth (0.05)0.09–0.14 mm long, spinulous, mostly inconspicuous teeth, supported by 2 ± projecting epidermal cells; tooth length leaf width ratio 0.13–0.3(0.5); midrib without teeth; transverse septa clearly apparent or absent; apex mostly obtuse or truncate and 2-dentate, sometimes more acute and 1-dentate; leaf sheath truncate to slightly auriculate, (1.3)1.9–2.4(2.9) mm long (including auricle and spine-cells); auricles / / of total sheath length, obtuse, serrulate or lacerate with 2–8 spine-cells on each side; intravaginal scales narrowly subulate, 0.5–0.88 mm long
sex Male
Male and female flowers solitary or aggregated, the male and the female mostly on different branch Male flower enclosed in a spathe, (1.2)1.9–2.5 (including spathe neck) 0.4–1 mm; spathe neck 0.5–0.6 mm long, tapering at the top and bearing mostly 2 brownish spine-cells at the apex; inner envelope protruding 0.16–0.32 mm above the anther; anther 1.0–2.4 0.36–1 mm, 4-sporangiate
sex Female
Female flower enclosed in a spathe, (1.1)1.5–2 (including spathe neck) × 0.4–0.6 mm; spathe neck reaching about halfway up the style, without spine-cells at apex; ovary 0.5–1.77 0.3–0.6 mm; style cylindric, with 2 long protruding stigmatic branch, the whole 0.8–1.3 mm long
Morphology Reproductive morphology Fruits
Fruit narrowly elliptic with persistent, thin, membranous gynoecial wall and remaining parts of style, stigma and spathe
Morphology Reproductive morphology Seeds
Seed (1.85)2.1–2.3(2.6) × (0.41)0.56–0.79 mm, ellipsoid-oblong; length width ratio 2.3–3.8; testa yellow or dull brown, with 14–20 longitudinal rows of areoles, 10–23 areoles in each row, irregular, mostly ± hexagonal, end walls raised.
Distribution
Zambia. An exclusively African species; also in Sierra Leone, Ivory Coast, Ghana(?), Nigeria, Cameroon, Central African Republic, Sudan, Congo, Rwanda, Uganda, Kenya and Angola.
Ecology
Ponds, ditches, swamps, streams; 1700 m.
Conservation
Conservation notes Very local within the Flora area, probably Lower Risk near threatened, but not threatened globally.
[FZ]

Sources

  • Angiosperm Extinction Risk Predictions v1

    • Angiosperm Threat Predictions
    • http://creativecommons.org/licenses/by/4.0

  • Flora Zambesiaca

    • Flora Zambesiaca
    • http://creativecommons.org/licenses/by-nc-sa/3.0

  • Flora of Tropical East Africa

    • Flora of Tropical East Africa
    • http://creativecommons.org/licenses/by-nc-sa/3.0

  • Herbarium Catalogue Specimens

    • 'The Herbarium Catalogue, Royal Botanic Gardens, Kew. Published on the Internet http://www.kew.org/herbcat [accessed on Day Month Year]'. Please enter the date on which you consulted the system.
    • Digital Image © Board of Trustees, RBG Kew http://creativecommons.org/licenses/by/3.0/

  • IUCN Categories

    • IUCN Red List of Threatened Species
    • http://creativecommons.org/licenses/by-nc-sa/3.0

  • Kew Backbone Distributions

    • The International Plant Names Index and World Checklist of Vascular Plants 2025. Published on the Internet at http://www.ipni.org and https://powo.science.kew.org/
    • © Copyright 2023 World Checklist of Vascular Plants. http://creativecommons.org/licenses/by/3.0

  • Kew Names and Taxonomic Backbone

    • The International Plant Names Index and World Checklist of Vascular Plants 2025. Published on the Internet at http://www.ipni.org and https://powo.science.kew.org/
    • © Copyright 2023 International Plant Names Index and World Checklist of Vascular Plants. http://creativecommons.org/licenses/by/3.0