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Phylum Magnoliophyta – Subphylum Seagrasses – Class Liliopsida – Subclass Alismatidae – Order Potamogetonales

Submerged or floating, annual or perennial, aquatic herbs, with monopodial or sympodial rhizomes rooting at the nodes. Roots unbranched. Leaves with sheathing base, eligulate. Squamules 2-many at each node, enclosed within the leaf sheath. Tannin cells present. Inflorescence a simple terminal spike. Flowers usually bisexual. Perianth present or absent. Stamens 2 or 4, anthers sessile each with 2 bilocular pollen sacs, longitudinally dehiscent; pollen grains globose to spherical or reniform. Carpels usually 3 or 4 (in some species considerably more), free; ovules solitary, pendulous, orthotropous or campylotropous. Fruit an achene, exocarp membranous or spongy, endocarp usually bony. Vegetative perennating organs sometimes present.

Taxonomic notes: A family of three genera which are widely distributed in temperate and subtropical regions, mostly in freshwater and sometimes in brackish or saline water. One genus, Ruppia, has marine representatives in southern Australia.

Ruppia has been placed in the monogeneric family Ruppiaceae (Hutchinson 1959, p. 558). However, more recent authors including Gamerro (1968), Thorne (1976) and Dahlgren (1980) have questioned the distinctions separating the Ruppiaceae from the Potamogetonaceae. In a revision of Ruppia in Australia, Jacobs & Brock (1982) consider Ruppia should be retained in the Potamogetonaceae and their treatment has been followed here.


DAHLGREN, R.M.T. (1980). A revised system of classification of the angiosperms. Bot. J. Linn. Soc. 80, 91–124.

GAMERRO, J.C. (1968). Observaciones sobre la biología floral y morfología de la Potamogetonacea Ruppia cirrohosa (Petag.) Grande (=R. spiralis L. ex Dum.). Darwiniana (B. aires) 14, 575–608.

HUTCHINSON, J. (1959). The families of flowering plants. II. Monocotyledons. 2nd edn. (Clarendon Press: Oxford.)

JACOBS, S.W.L. & BROCK, M.A. (1982). A revision of the genus Ruppia (Potamogetonaceae) in Australia. Aquat. Bot. 14, 325–337.

THORNE, R.F. (1976). A phylogenetic classification of the Angiospermae. Kw!. Biol. 9, 35–106.

The Marine Benthic Flora of Southern Australia Part I complete list of references.

Author: H.B.S. Womersley

Publication: Womersley, H.B.S. (31 May, 1984)
The Marine Benthic Flora of Southern Australia
Part I
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