Hippuridaceae Link
Mare's tail family.
Hippuridaceae, mares tail family.
Vegetative morphology. Plants perennial herbs; (4–)10–50(–150) cm high; with heterophyllous leaves in whorls. Ground-level or under-ground stems horizontal (and semi-horizontal stems, rooting in soft substrates); rhizomatous (but rhizomes are rarely found on herbarium specimens); elongate, or compact. Aerial stems erect; glabrous. Leaves heterophyllous (particularly when plants grow in shallow water), or not heterophyllous (submerged plants); distributed along the stems; whorled; existing for a single season or less. Petioles absent. Blades adaxial surface glabrous. Blades abaxial surface glabrous.
Reproductive morphology. Flowering stems absent. Inflorescence spicate; axillary. Pedicels absent. Flowers small, less than 5 mm in diameter or length; zygomorphic (very reduced). Perianth absent. Flowers unisexual. Stamens 1. Gynoecia inferior. Carpels monomerous (pseudo-monomerous); 1. Placentation apical. Fruit a nut; indehiscent.
Chromosome information. 2n = 32. Supposed basic chromosome number of family 4x.
Notes. The two species H. vulgaris and H. tetraphylla L.f. are related but differ both in several morphological features (e.g., H. vulgaris has a mean of eight acute leaves in each whorl, H. tetraphylla has a mean of four short, obtuse leaves in each whorl) and in ecology. Hippuris vulgaris occurs mainly in fresh water but also transgresses into brackish waters.
Cite this publication as: ‘S.G. Aiken, M.J. Dallwitz, L.L. Consaul, C.L. McJannet, L.J. Gillespie, R.L. Boles, G.W. Argus, J.M. Gillett, P.J. Scott, R. Elven, M.C. LeBlanc, A.K. Brysting and H. Solstad. 1999 onwards. Flora of the Canadian Arctic Archipelago: Descriptions, Illustrations, Identification, and Information Retrieval. Version: 29th April 2003. http://www.mun.ca/biology/delta/arcticf/’. Dallwitz (1980) and Dallwitz, Paine and Zurcher (1993, 1995, 2000) should also be cited (see References).