Elatinaceae Dumort.

Milliken, W., Klitgard, B. and Baracat, A. (2009 onwards), Neotropikey - Interactive key and information resources for flowering plants of the Neotropics. http://creativecommons.org/licenses/by/3.0

Morphology General Habit

Shrubs or herbs (annual or perennial), often aquatic or semiaquatic, with resinous latex, glabrous or pubescent with uni- or multicellular, unbranched trichomes, these sometimes gland -tipped, stems often rooting at the nodes

Morphology Leaves

Leaves opposite or whorled, submerged in some of the aquatic species, stipules present, interpetiolar, free, small, scarious, lamina simple, entire, serrate or crenulate, multicellular extrafloral glands often present along leaf margins, pinnately veined

Morphology Reproductive morphology Flowers

Flowers solitary or in few-flowered axillary cymes, small, actinomorphic, hermaphroditic, disk absent, sepals 2-5(6), imbricate, free or connate in lower half, petals 2-5(6), imbricate, free, persistent, stamens opposite the sepals, of same number or twice as many as sepals, free, equal, anthers bithecal, dorisfixed, versatile, introrse, with longitudinal dehiscence, pollen tricolporate, ovary superior, 2-5(6)-locular, locules connate, each with numerous ovules, anatropous, placentation axillary or basal, styles same number as  locules, short, free, apical, stigma capitate, papillose

Morphology Reproductive morphology Fruits

Fruit capsular, with septicidal dehiscence

Morphology Reproductive morphology Seeds

Seeds numerous, exarillate, without endosperm, embryo straight or curved, cotyledons short X=6 or 9.

Note

Notes on delimitation: Elatinaceae contains only two genera: Elatine L. and Bergia L.  The family has historically been considered closely related to the Clusiaceae.  However, recent molecular phylogenetic studies suggest that it is sister to Malpighiaceae, in the order Malpighiales. Some members of Elatine are cultivated in aquaria, and a few species of Bergia employed in traditional medicine.  Otherwise the family is of little economic importance. The introduced Bergia capensis L. occurs in various low elevation wetland sites, including rice fields.  It is noteworthy in possessing dimorphic roots, with those of plants growing in water being chlorophyllous and free floating whereas those of terrestrial plants being white and sturdy. The majority of the nearly 25 species of Bergia occur in the Old World, with the center of diversity in southern Africa. Elatine is widely distributed throughout the world, with most of its 25 species occurring in the northern hemisphere. Although the Neotropical species are strictly aquatic to semiaquatic herbs, some Old World species of Bergia are shrubs that occur in arid environments. Number of genera: Two: Bergia and Elatine.

Distribution

Elatine: Approximately seven aquatic species distributed sporadically throughout the Neotropics mostly in high-elevation, temperate, standing bodies of waters but rarely in tropical or subtropical habitats at lower elevations. Bergia: Two aquatic to semiaquatic species with limited distribution in the Neotropics and a third species approaching the area: B.capensis L., a native to southern Africa, is occasionally naturalized in tropical wetlands in at least Cuba, Mexico, Peru and Ecuador; the little-known B.arenaroides Fenzl is endemic to Brazil; although not known from the Neotropics proper, B.texana Seub. ex Walp. approaches the region in subtropical northern Mexico, with extralimital records from the states of Sonora and Tamaulipas. Both genera are native to the Neotropics; Bergia has an additional naturalized species.

Diagnostic

Aquatic or semiaquatic herbs (at least in the Neotropical species). Distinguishing characters (always present): Leaves opposite or whorled, stipulate, simple. Flowers small, actinomorphic, hermaphroditic, sepals, 2-5(6), free or united at the base, petals 2-5(6), free, stamens equal the number of sepals/petals or twice as many. Ovarysuperior, 2-5(6)-locular, loculesconnate, each with numerous ovules. Fruit a septicidalcapsule. Key differences from similar families: Elatine can be confused with various other aquatics having reduced, inconspicuous flowers, but is distinguished by the combination of opposite, stipulate leaves; flowers with 2 to 4 petals and sepals and a superiorovary; and septicidal capsules with numerous reticulate seeds. Key to genera of Neotropical Elatinaceae 1. Flowers with 5 (6) sepals and petals; sepals possessing a conspicuous mibrid, apex acute and often with a sharp tip ... Bergia 1. Flowers with 2-4 sepals and petals; sepals without a distinct midrib, apex obtuse... Elatine

Elatinaceae, B. Verdcourt. Flora of Tropical East Africa. 1968

Morphology General Habit

Herbs or small shrubs, sometimes aquatic

Morphology Leaves

Leaves opposite or verticillate, simple or submerged leaves sometimes much divided, entire or serrate; stipules present, paired

Morphology Reproductive morphology Flowers

Flowers small, regular, hermaphrodite, axillary, solitary, cymose, fasciculate or in glomerules, occasionally cleistogamous

Morphology Reproductive morphology Flowers Calyx

Sepals (2–)3–5(–6), free, imbricate, not nerved or 1-nerved, mostly with pellucid margins

Morphology Reproductive morphology Flowers Corolla

Petals (2–)3–5(–6), hypogynous, imbricate, persistent

Morphology Reproductive morphology Flowers Androecium

Stamens as many as and alternate to twice as many as the petals, free, hypogynous; anthers dithecous, opening by longitudinal slits

Morphology Reproductive morphology Flowers Gynoecium

Ovary superior, (2–)3–5-locular, with axile placentation; ovules numerous; styles (2–)3–5, free

Morphology Reproductive morphology Fruits

Fruit a septicidal capsule

Morphology Reproductive morphology Seeds

Seeds straight or curved, without or with very little endosperm; embryo straight or curved, with short cotyledons

Elatinaceae, H. Wild. Flora Zambesiaca 1:2. 1961

Morphology General Habit

Herbs or low shrubs

Morphology Leaves

Leaves opposite or verticillate, simple, entire or toothed; stipules present, paired

Morphology Reproductive morphology Flowers

Flowers small, actinomorphic, bisexual, axillary, solitary or in small cymes, fascicles or verticillate clusters

Morphology Reproductive morphology Flowers Calyx

Sepals 3–5, imbricate

Morphology Reproductive morphology Flowers Corolla

Petals 3–5(6), imbricate, persistent

Morphology Reproductive morphology Flowers Androecium

Stamens as many, or twice as many as the sepals; anthers 2-thecous, opening by longitudinal slits

Morphology Reproductive morphology Flowers Gynoecium

Ovary superior, 3–5-locular, multiovulate; styles 2–5, free

Morphology Reproductive morphology Fruits

Fruit a septicidal capsule

Morphology Reproductive morphology Seeds

Seeds without endosperm, straight or curved; embryo with short cotyledons