Cymodoceaceae Vines

This family is accepted.


Haigh, A. (2009). Neotropical Cymodoceaceae.


Habit : Herbs, marine aquatics, submerged, perennial ; rhizomes present, creeping. Leaves alternate ( distichous ), simple , with open basal sheath and small ligule , numerous axillary intravaginal squamules present; stomata and trichomes absent. Inflorescences borne at end of short erect shoots, usually of solitary flowers, rarely in cymes. Flowers unisexual (plants dioecious ); perianth absent. Staminate flowers: sessile or stalked; androecium with 2 stamens, the stamens fused back to back with apical prolongation. Pistillate flowers: gynoecium apocarpous, the ovaries superior , the carpels 2, the styles long, slender, often branched, the stigmas inconspicuous in Halodule Endl. or of two stigmatic stout stylodia in Syringodium Kütz.; placentation apical, the ovules 1 per carpel . Fruits indehiscent , small; endocarp stony.

General Description
Notes on delimitation
  • The Cymodoceaceae are placed in the Alismatales in the APGIII classification system.
  • They were previously placed in the Najadales by Dahlgren et al (1985) and also by Cronquist (1981).
Number of genera

See above

  • Native.
General notes
  • Commonly known as sea-grasses or manatee grasses.
  • Cymodoceaceae occur in shallow, coastal, tropical or subtropical waters.
  • They can form extensive submarine meadows in shallow, clear waters with minimal wave action.
  • Some are important in the stabilization of shallow marine sediments, nutrient recycling, and as food sources for grazing marine animals.
Distribution in the Neotropics

A sub cosmopolitan family of 5 genera and c.16 species.  Two genera comprising 5 species occur in the Neotropics.

  • Halodule (4 species in Neotropics).
  • Syringodium (1 species in Neotropics).
Distinguishing characters (always present)
  • Herbs.
  • Submerged marine aquatics growing in shallow waters.
  • Leaves alternate (distichous), simple.
  • Plants dioecious; perianth absent; stamens 2, partially fused back to back.
Useful tips for generic identification

Key to genera of Neotropical Cymodoceaceae

1. Leaf blade distinctly terete; many flowers in conspicuous cymose inflorescences — Syringodium
1. Leaf bladelinear, flat; inflorescence 1-flowered or 2 flowers resembling a single flower — Halodule

Important literature

Cronquist, A. 1981. An Integrated System of Classification of Flowering Plants. Columbia University Press, New York.

Dahlgren, R. M. T., Clifford, H. T., & Yeo, P. F. 1985. The Families of the Monocotyledons. Springer, Berlin.

Hartog, C. Den, 1970. The sea-grasses of the world. Verhandl. Kon. Ned. Akad. Wetensch. Nat. 59(1): 1-275.

Kuo, J. & McComb, A.J. 1998. Cymodoceaceae. In: K. Kubitzki (ed.), The families and genera of vascular plants 4: 133-140. Springer Verlag, London.

Stevenson, D.W., 2004. Cymodoceaceae. Pp. 433-434. In: Smith, N., Mori, S.A., Henderson, A., Stevenson, D.W. & Heald, S.V. (eds.). Flowering Plants of the Neotropics. New York Botanical Garden, Princeton University Press, Princeton.


Cymodoceaceae, Henk Beentje. Flora of Tropical East Africa. 2002

Morphology General Habit
Marine plants, perennial, dioecious, glabrous; rhizome creeping; vessel elements absent
Morphology Leaves
Leaves distichous or spiral; leaf-sheath amplexicaul, with 2 apical auricles, ligulate; blade linear with several parallel nerves, in between which tannin dots and dashes are visible
Morphology Reproductive morphology Flowers
Flowers terminal and solitary on a short branch, or in cymose inflorescences, sessile or stalked, small, water-pollinated; tepals absent Pistillate flowers of 2 free ovaries; ovule 1, pendulous Staminate flowers consisting of 2 anthers, these 4-locular, partially connate, dehiscing by extrorse slits; pollen thread-like, without exine
sex Male
Staminate flowers consisting of 2 anthers, these 4-locular, partially connate, dehiscing by extrorse slits; pollen thread-like, without exine
sex Female
Pistillate flowers of 2 free ovaries; ovule 1, pendulous
Morphology Reproductive morphology Fruits
Fruit an indehiscent nutlet; seed 1; endosperm absent


M. Thulin et al. Flora of Somalia, Vol. 1-4 [updated 2008]

Morphology General Habit
Dioecious, marine perennials with creeping, monopodially or sympodially branched rhizomes; rhizome leafy or with scale leaves, herbaceous and rooting at the nodes or woody and rooting from the internodes
Morphology Leaves
Leaves distichous, with distinct blade and sheathing base; sheath ligulate, auriculate; blade 3- to several-nerved, narrowly or broadly ribbon-like or, rarely, terete and subulate
Morphology Reproductive morphology Inflorescences
Flowers usually solitary and terminal on short erect shoots or on branches of erect shoots, but forming cymose inflorescences in Syringodium
Morphology Reproductive morphology Flowers Perianth
Perianth absent
Morphology Reproductive morphology Flowers Pollen
Pollen grains filamentous and tightly coiled within the anther
Morphology Reproductive morphology Flowers
Female flowers sessile or shortly stalked, consisting of two free carpels, each carpel having either a simple, long style (Halodule) or a style divided into 2 or 3 slender stigmas, and containing one pendulous ovule Male flowers subsessile or stalked, consisting of 2 extrorsely dehiscent, 2-thecous anthers ± dorsally united and attached either at the same height or one slightly above the other (Halodule)
Morphology Reproductive morphology Fruits
Fruit a 1-seeded nut, indehiscent, either with a stony endocarp or viviparous
Morphology Reproductive morphology Seeds
Seed without endosperm.
Family of five genera and about 20 species; for the most part occurring in tropical and subtropical oceans.

Cymodoceaceae Vines appears in other Kew resources:

First published in Stud. Text-book Bot. 2: 553. 1895 [Mar 1895] (1895)

Accepted by

  • APG IV (2016)


Flora of Somalia

  • Cuf. Enum.:1200–1201 (1968)
  • Flora Somalia, Vol 4, (1995) Author: by G. Sartoni [updated by M. Thulin 2008]

  • Flora of Somalia

    Flora of Somalia

  • Flora of Tropical East Africa

    Flora of Tropical East Africa

  • Kew Names and Taxonomic Backbone

    The International Plant Names Index and World Checklist of Selected Plant Families 2022. Published on the Internet at and
    © Copyright 2017 International Plant Names Index and World Checklist of Selected Plant Families.

  • Neotropikey

    Milliken, W., Klitgard, B. and Baracat, A. (2009 onwards), Neotropikey - Interactive key and information resources for flowering plants of the Neotropics.