Lagarosiphon Harv.

First published in J. Bot. (Hooker) 4: 230 (1841)
This genus is accepted
The native range of this genus is Tropical & S. Africa, Madagascar.

Descriptions

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

Morphology General Habit
Freshwater herbs, perennial, submerged except for the flowers at anthesis, dioecious
Morphology Roots
Roots unbranched
Morphology Stem
Stems elongate, cylindrical, the basal part persistent, rhizomatous with distant axillary branch, densely leaved at nodes, internodes lengthening afterwards
Morphology Leaves
Leaves alternate, subopposite or subverticillate, sessile, linear to linear-lanceolate, often recurved; margins green or with several longitudinal rows of translucent fibres, serrulate or denticulate; apex with 2 spine cells
Morphology General Scales
Intravaginal scales 2, axillary, minute
Morphology Reproductive morphology Inflorescences
Inflorescences axillary, solitary, sessile and unisexual-Male spathes consisting of 2 united bract, ovate or obovate, compressed or cup- shaped, toothed; receptacle with numerous stalked flower buds that break off and rise to the water surface where they open
sex Male
Male flowers with a perianth of 2 whorls, each with 3 segments, reflexed at anthesis, the outer slightly narrower; stamens 3, filaments expanding and stretching out parallel to water surface with anther at right angles; staminodes 2–3, erect, longer than stamens, papillate and usually coloured above, joined at top, acting as a sail
sex Female
Female flowers sessile, but hypanthium exserted near apex of spathe, lengthening so that the flower bud reaches the water surface; perianth segments 6, all alike, or the outer slightly smaller, spreading and floating; staminodes 3, minute, filiform; ovary unilocular, with 3 parietal placentas; styles 3, each divided above into 2 long papillate, often brightly coloured stigma; ovules 5–30, orthotropous Female spathes 1- flowered, comprising 2 united bract, narrowly ovate to oblong or cylindrical, entire or toothed
Morphology Reproductive morphology Fruits
Capsule ovate, extended into a beak which protrudes and tears the spathe-valves; pericarp honeycombed, becoming mucilaginous and bursting irregularly and so dispersing the seed
Morphology Reproductive morphology Seeds
Seeds 5–30, ellipsoidal, with short stipe at base, tapering at apex, densely ribbed or honeycombed, buoyant at first, sinking later.
Distribution
A genus of 9 species with 8 in Sub-Saharan Africa and 1 endemic to Madagascar. L major is adventive, often invasive, in Europe and New Zealand.
Recognition
All Lagarosiphon species can be identified without flowers. A lens ( 12 magnification) is required to see details of the leaf margins, but a microscope is necessary to see the epidermal cells and details of the central area. Polarized light makes the observation of fibre rows easier.
[FZ]

Hydrocharitaceae, David Simpson. Flora of Tropical East Africa. 1989

Morphology General Habit
Dioecious, submerged, freshwater, perennial herbs
Morphology Roots
Roots simple, adventitious, without root hairs, arising from nodes
Morphology Stem
Stems elongate, stoloniferous or erect, filiform to terete, simple or branched from axils; branches 1 per axil
Morphology Leaves
Leaves sessile, spirally arranged, subopposite or in whorls, linear to lanceolate, shortly acuminate to subobtuse, patent to strongly recurved, firm or flaccid, with 2 apical spines, often with 2 bands of sclerenchyma fibres on either side of midrib and 2–6 rows of submarginal sclerenchyma fibres; venation reduced to midrib only; margins green or hyaline, denticulate Nodal scales 2 per leaf, linear to widely ovate, with entire or papillose margins
Morphology Leaves Stipules
Stipules 0
Morphology Reproductive morphology Flowers
Flowers unisexual Female flower: sepals and petals 3, elliptic to ovate, obtuse or cucullate, usually reflexed at anthesis; staminodes 3, minute, linear; ovary 1-locular, placentation parietal; ovules 5–30, orthotropus; perianth-tube filiform, exerted laterally from the ovary near apex of the spathe, carrying perianth to the water surface; styles 3; stigmas 6, 2 per style, linear, papillose Male flowers shortly pedicellate, becoming detached and floating before anthesis; sepals and petals 3, oblong-ovate to ovate, obtuse or cucullate, usually reflexed at anthesis; stamens 3; anthers 4-thecous, fixed at right-angles to the filaments; filaments filiform, spreading horizontally; staminodes often present, 3, filiform, papillose, longer than the stamens, usually joined at the apex and functioning as a sail
sex Male
Male spathe solitary in leaf-axil, sessile, ovate to suborbicular, toothed, containing up to 40 flowers Male flowers shortly pedicellate, becoming detached and floating before anthesis; sepals and petals 3, oblong-ovate to ovate, obtuse or cucullate, usually reflexed at anthesis; stamens 3; anthers 4-thecous, fixed at right-angles to the filaments; filaments filiform, spreading horizontally; staminodes often present, 3, filiform, papillose, longer than the stamens, usually joined at the apex and functioning as a sail
Morphology Reproductive morphology Inflorescences
Female spathe solitary in leaf-axil, sessile, narrowly ovate to ovate, toothed, 1-flowered Male spathe solitary in leaf-axil, sessile, ovate to suborbicular, toothed, containing up to 40 flowers
sex Female
Female spathe solitary in leaf-axil, sessile, narrowly ovate to ovate, toothed, 1-flowered Female flower: sepals and petals 3, elliptic to ovate, obtuse or cucullate, usually reflexed at anthesis; staminodes 3, minute, linear; ovary 1-locular, placentation parietal; ovules 5–30, orthotropus; perianth-tube filiform, exerted laterally from the ovary near apex of the spathe, carrying perianth to the water surface; styles 3; stigmas 6, 2 per style, linear, papillose
Morphology Reproductive morphology Fruits
Fruit ovate, beaked at apex, pericarp smooth, irregularly dehiscent
Morphology Reproductive morphology Seeds
Seeds narrowly ellipsoid to ellipsoid, smooth, with short stipe at base, attenuate at apex.
[FTEA]

M. Thulin et al. Flora of Somalia, Vol. 1-4 [updated 2008] https://plants.jstor.org/collection/FLOS

Morphology General Habit
Perennial freshwater herbs, dioecious
Morphology Roots
Roots simple, arising from nodes, without root hairs
Morphology Stem
Stems simple or 1-branched from axils
Morphology Leaves
Leaves sessile, spirally aranged or in whorls, linear to lanceolate, denticulate, 1-veined
Morphology Reproductive morphology Inflorescences
Male inflorescence axillary, sessile, many-flowered
Morphology Reproductive morphology Flowers Androecium Stamens
Stamens 3; anthers fixed at right-angles to the horizontally spreading filaments; staminodes often present, joined at the apex and acting as a sail
Morphology Reproductive morphology Flowers
Female flowers solitary; perianth tube filiform, exserted laterally from the ovary near apex of the spathe, lengthening so that the flower bud reaches the water surface; tepals 6; staminodes 3, minute Male flowers becoming detached and floating before anthesis; tepals 6
Morphology Reproductive morphology Flowers Gynoecium Ovary
Ovary with 5–30 ovules; styles 3; stigmas 6, linear
Morphology Reproductive morphology Fruits
Capsule ovate, beaked at the apex, irregularly dehiscent
Morphology Reproductive morphology Seeds
Seeds ellipsoid.
Distribution
Nine species in Africa and Madagascar. One species, L. major (Ridley) Moss, also introduced in Europe and New Zealand.
[FSOM]

Sources

  • Flora Zambesiaca

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

    • Flora of Somalia
    • 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.
  • 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