PBIO 250 Lecture Notes
James L. Reveal
Norton-Brown Herbarium, University of Maryland
II. LILIOPSIDA Scop., 1761 - Be sure to go to the "Next Section" for all of the information on Liliopsida. See Cronquist's "Phylogenetic Tree" of the monocots and the summary from the University of Wisconsin
Selected Families of Angiosperms: Alismatidae
ALISMATIDAE Takht., 1967: 4 orders, 16 families and about 500 species. The smallest (in terms of species) and most primitive group with monocotyledonous features according to Cronquist. Plants either apocarpous and sometimes monocarpous flowers or more or less aquatic, often both and always herbaceous but never thalloid. The taxon has trinuceate pollen, rather than binucleate pollen and therefore the Alismatidae is not on the main branch of monocot evolution but represents a relictual side-branch. Summary from the University of Wisconsin
Alismatales Dumort., 1829
Alismataceae Vent., 1799: Aquatic or wetland herbs with bisexual flowers with 3 green sepals and 3 petals bearing an apocarpous gynoecium with many free carpels resulting in a spiral or ring of achenes. CA3 CO3 A6-many GS6-many. 12 genera, 80 species. Cosmopolitan, especially in north temperate regions. Pollen often multiporate. An important group for waterfowl. Full description from Watson & Dallwitz; family synonymy from Reveal; list of genera from Kew; family synopsis from the University of Hawaii.
Hydrocharitales Dumort., 1829
Hydrocharitaceae Juss., 1789: Aquatic herbs of fresh or marine waters with simple, usually ribbonlike leaves, and uni- or bisexual flowers with an inferior compound ovary. CA3 CO3 A2-many GI (3-6). 18 genera, 110 species. Cosmopolitan. Three subfamilies commonly recognized: Hydrocharitoideae Eaton, Thalassioideae Aschers. & Gürcke and Halophiloideae Aschers. & Gürcke. Many fresh-water species are important for fish and waterfowl habitat. Egeria and Elodaea are sometimes cultivated for use in fish tanks. Thalassia and Halophila are marine genera with pollen in thread-like chains. Full description from Watson & Dallwitz; family synonymy from Reveal; list of genera from Kew; family synopsis from the University of Hawaii.
Najadales Rchb., 1828
Potamogetonaceae Dumort., 1829: Aquatic herbs with both submerged and floating leaves and 4-merous flowers with a superior gynoecium of 1 to 4 distinct carpels. CA0 or 4 CO0 A1-4 GS1-4. 4 genera (Potamogeton, Coleogeton, Stuckenia and Groenlandia), 90 species. Cosmopolitan, mostly in temperate regions. Potamogeton is often critical for fish and waterfowl habitat, the drupelets or achenes being used for food especially by ducks. The genus Ruppia (Ruppiaceae) is sometimes included within Potamogetonaceae. Full description from Watson & Dallwitz; family synonymy from Reveal; list of genera from Kew; family synopsis from the University of Hawaii.
Zosteraceae Dumort., 1829: Aquatic graminoid herbs of marine waters with creeping rhizomatous stems bearing unisexual flowers lacking a perianth. CA0 CO0 A1 G0 or CA0 CO0 A0 G(2). 3 genera, 19 species. Warm and cool water coastal regions. A major ecological indicator of pollution in shallow marine water habitats. Important for fish and waterfowl. The pollen grains have the same density as seawater so that pollination occurs underwater with the feathery stigma capturing the grain. Sometimes referred to Potamogetonaceae. Full description from Watson & Dallwitz; family synonymy from Reveal; list of genera from Kew.
Next Series of Lecture Notes:
Selected Families of Angiosperms: Arecidae
Last revised: 24 Nov 1997; last revised: 2 Feb 1999