Arecales Bromhead, 1840
Arecaceae Schultz-Sch., 1832: Woody shrubs or trees with large, often fan-shaped or pinnately-compound leaves with sheathing bases and large, spathe-bearing, paniculate inflorescences bearing small flowers. CA3 CO3 A6 GS3 or (3) or CA3 CO3 A6 G0 and CA3 CO3 A0 GS3 or (3). 207 genera, 2675 species. Mainly tropical and subtropical regions. The palm family (also known as Palmae) is generally divided into six subfamilies (Coryphoideae Burnett, Nypoideae Engl., Calamoideae Beilschm., Arecoideae Burnett and Phytelephantoideae Drude), but only one is occasionally recognized as a distinct family (Nypaceae). Sabal and Washingtonia are two of the native genera in the continental United States. Copernicia is the source of carnauba wax, Phoenix is the date palm, Lodoicera has the largest seeds known, rattan comes from Korthalsia. Areca, Cyrtostachys, Dypsis, Howeia and Roystonea are frequently cultivated, Cocus is the coconut, and Phytelephas is the vegetable ivory. Full description from Watson & Dallwitz; family synonymy from Reveal; list of genera from Kew; family synopsis from the University of Hawaii.
Arales Dumort., 1829
Araceae Juss., 1789: Herbs or sometimes shrubs of mainly wet places with a spadix subtended by a spathe bearing small or minute flowers that often lack a perianth. CA0 or 4-6 CO0 or 4-6 A4-6 GS (2-3). 109 genera, 3075 species. Widespread but mainly tropical and subtropical. Divided into 7 subfamilies (Gymnostachyoideae, Orontioideae Müll. Berol., Pothoideae Engl., Monsteroideae (Schott) Engl., Lasioideae Engl., Calloideae Endl. and Aroideae Arn.) Many cultivated for their leaves (Anthurium, Monstera, Rhaphidophora, Dieffenbachia, Philodendron, Caladium, Arum), but more important as food plants in the tropics. Some are poisonous. Calla is sometimes cultivated for its inflorescences. Pistia is aquatic and often fouls waterways. Acorus (Acoraceae) has been traditionally placed in Araceae, but now regarded correctly as the only member of its own family, order (Acorales) and superorder (Acoranae). Full description from Watson & Dallwitz; family synonymy from Reveal; list of genera from Kew; family synopsis from the University of Hawaii.
Lemnaceae Gray, 1821: Small or minute floating or submerged aquatic herbs rarely producing flowers that lack a perianth. CA0 CO0 A1 G0 or CA0 CO0 A0 G1. 4 genera, 37 species. Widespread but mainly in temperate regions. Divided into two subfamilies: Lemnoideae Bab. and Wolffioideae Engl. The duckweed is the genus Lemna (12 species); it is an important food to waterfowl and fish. Spirodela (4 species) has numerous roots and is the least reduced in the family. Wolffiella (10 species) is a rootless, ligulate thalloid. Wolffia (11 species), the watermeals, include the smallest known flowering plants. Wolffia arhiza is a rootless thalloid about 1.5 mm long; W. brasilensis and W. microscopica are sometimes less than 1 mm long. Full description from Watson & Dallwitz; family synonymy from Reveal; list of genera from Kew; family synopsis from the University of Hawaii. See the wonderful review of the duckweeds by Wayne Amstrong of Wayne's World