Neotropical Ceratophyllaceae

Jon L.R. Every

Reading University, Reading, U.K.


Submersed aquatic, rootless, glabrous herbs. Leaves whorled, simple, finely divided (often dichotomously branched), lobes often toothed, petiole inconspicuous or lacking. Inflorescences extra-axillary and alternating with leaves, spikes or racemes. Flowers solitary, unisexual, monoecious, actinomorphic, pedicels short or flowers sessile, bracts foliaceous; calyx of (7)9-12(15) toothed sepals; corolla lacking; stamens 3-many, spirally arranged, free of perianth, filaments short, anthers adnately fixed, dehiscing via full-length slits; ovary superior, monomerous, style 1, persistent, spiny, occasionally bifid. Fruits achenes, papillose, spiny or smooth. Seeds 1, tiny.

Notes on delimitation

  • Recently placed in an order of its own - the Ceratopyllales with molecular evidence positioning Ceratophyllaceae as probable sister to eudicots (APG III, 2009).
  • The development and complicated make-up of the perianth has led the family to be compared with the ANITA clade (excluding Nymphales).

Distribution in the Neotropics

  • Throughout the Neotropics in non-marine aquatic habitats.

Distinguishing characters (always present)

  • Aquatic herbs.
  • Leaves in whorls of 3-10.
  • Roots lacking.
  • Stamens ca. 3-45.
  • Styles persistent on fruits.

Key differences from similar families

Number of genera

  • One genus Ceratophyllum L. with three of the six cosmopolitan species: C. demersum L., C. submersum L. and C. muricatum (Cham.) occurring in the Neotropics.

Useful tips for generic identification

  • Native and naturalizing; has become a problem weed harbouring vectors of diseases threatening human health and choking the waterways in which they inhabit.

General notes


Important literature

Akitoshi, I., Akiko, S. and Hideaki, O.2003. Floral development and phyllotactic variation in Ceratophyllum demersum (Ceratophyllaceae). American Journal of Botany 90(8):1124-1130.

APG III. 2009. An update of the Angiosperm Phylogeny Group classification for the orders and families of flowering plants. Botanical Journal of the Linnean Society 161(3): 105-121.

Campbell, L. M. 2004. In: Smith, N., Mori, S. A., Henderson, A., Stevenson, D. W. and Heald, S. V. (eds). Flowering Plants of the Neotropics. Pp. 96-7. The New York Botanical Garden, Princeton University Press, Princeton.

Les, D. 1993. In: Kubitzki, K., Rohwer, J. G., & Bittrich, V. (eds.), The Families and Genera of Vascular Plants vol. II. Flowering Plants: Dicotyledons, Magnoliid, Hamamelid and Caryophyllid Families. Pp 246-250. Springer Verlag, Berlin.

Mabberley, D. J. 2008. Mabberley's Plant-book. 3rd ed. Pp. 168-9. Cambridge University Press, Cambridge.

Stevens, P. F. 2008. Angiosperm Phylogeny Website. Version 9 onwards.

Watson, L. and Dallwitz, M.J. (1992 onwards). The Families of Flowering Plants: Descriptions, Illustrations, Identification, and Information Retrieval. Version 3rd March 2009.

How to cite

Every, J.L.R. (2010). Neotropical Ceratophyllaceae. In: Milliken, W., Klitgård, B. & Baracat, A. (2009 onwards), Neotropikey - Interactive key and information resources for flowering plants of the Neotropics.