Lythraceae J.St.-Hil.

Lythraceae, A. Fernandes. Flora Zambesiaca 4. 1978

Morphology General Habit

Annual or perennial (sometimes marshy or aquatic) herbs, suffrutices, shrublets, shrubs or trees

Morphology Leaves

Leaves simple, entire, 1-nerved or ± distinctly penninerved, decussate, sometimes verticillate, rarely alternate; stipules 0 or 2–10 or more, small, subulate, axillary

Morphology Reproductive morphology Flowers

Flowers bisexual, actinomorphic or very rarely zygo-morphic, (3)4–5(6–16)-merous, homomorphic or often di-trimorphic

Morphology Reproductive morphology Inflorescences

Inflorescence various from single axillary flowers to fasciculate, cymose or paniculate; pedicels usually bracteolate

Morphology Reproductive morphology Flowers Calyx

Calyx persistent, tubular, urceolate or campanulate, the lobes alternating often with ± developed appendages in the sinuses

Morphology Reproductive morphology Flowers Corolla

Petals inserted in the calyx-tube, as many as and alternating with the calyx-lobes, sometimes few or 0, often clawed, membranous, corrugated and imbricate in the bud, equal or sometimes unequal

Morphology Reproductive morphology Flowers Androecium

Stamens numerous (32–200) in the primitive woody genera, often as many as the calyx-lobes, sometimes fewer (2 or 1) in the more advanced herbaceous ones, equal or sometimes very unequal (in heterostylous plants), inserted on the calyx-tube; filaments free; anthers 2-locular, bent inwards in the bud, dorsifixed and versatile, rarely basifixed (Pleurophora and Crimea, not from FZ area), dehiscing by longitudinal slits

Morphology Reproductive morphology Flowers Nectaries

Disk absent or very small, cupular or unilateral

Morphology Reproductive morphology Flowers Gynoecium

Ovary usually free, sessile or stipitate, 2–6-locular or 1-locular (Cryptotheca); placentation axile, rarely basal, sometimes the central axis not reaching to the top of the ovary; style absent, short or elongate and flexuous; stigma capitate or punctiform, rarely 2-lobed; ovules numerous to 2, small, anatropous, ascending

Morphology Reproductive morphology Fruits

Fruit mostly a capsule included in the calyx-tube or ± exserted, indehiscent or opening loculicidally or septicidally by valves or by a transverse lid or irregularly, with the placentas forming a central column

Morphology Reproductive morphology Seeds

Seeds 2-numerous, various in form, small, sometimes winged; embryo straight, with endosperm; cotyledons flat or rarely convolute

Graham, S. & Cavalcanti, T.B. (2009). Neotropical Lythraceae.

Morphology

Description

Trees, shrubs or herbs, younger stems often quadrangulate.  Leaves opposite, less often whorled or subalternate, simple , entire , estipulate, colleters present in leaf axils; blades membranous or coriaceous , venation brochidodromous .  Inflorescences indeterminate, racemes, cymes, or clusters, rarely flowers solitary; pedicels with prophylls (bracteoles).  Flowers actinomorphic or zygomorphic , perfect, perigynous , (4)- 4-6 -(16)- merous ; floral tube campanulate to tubular, often conspicuously veined, persistent except in Lafoensia; sepals valvate , petals (0)-4-6(-many), inserted on the inner rim of floral tube, alternating with sepals, crinkled, pinnately veined, caducous ; stamens diplostemonous, sometimes reduced to a single whorl; gynoecium syncarpous, nectariferous tissue present or absent; style simple , slender, commonly exserted , stigma capitate or punctiform; ovary superior , infrequently semi-inferior, (2)-2-4(-many) locular, septa incomplete at apex or vestigial, reduced to thin threads, placentation axile , or globose and nearly free -central.  Fruits dry, thin or thick-walled capsules enclosed by persistent floral tube, dehiscing loculicidally, septicidally, or splitting irregularly.  Seeds numerous, obpyramidal, or oblong to obovoid and concave-convex, or bilaterally lenticular- compressed , winged or not, with inverted epidermal trichomes in seed coat; embro straight, cotyledons planar, auriculate or cordate , oily.  x = 8.

General Description

Notes on delimitation

• Based on molecular evidence, the Combretaceae is sister to the Lythraceae and the Onagraceae. The three families constitute a major lineage of the Myrtales. 
• Recent molecular work has led to the expansion of the family to include the satellite families Sonneratiaceae, Duabangaceae, Punicaceae and Trapaceae.

Number of genera

• 15 native genera: Adenaria, Ammannia, Crenea, Cuphea, Diplusodon, Ginoria (including Haitia), Heimia, Lafoensia, Lourtella, Lythrum, Nesaea, Pehria, Physocalymma, Pleurophora, Rotala.

Status

• Three non-native genera cultivated in the Neotropics: Lagerstroemia (crape myrtle), Lawsonia (henna), Punica (pomegranate).

General notes

• Waiting publication: Haitia synonymized with Ginoria in Graham, S. A. (2009, in press).  Revision of the Caribbean Genus Ginoria (Lythraceae), including Haitia from Hispaniola.  Ann. Missouri Bot. Garden.

Distribution

Distribution in the Neotropics

• Adenaria Kunth (1/1 sp.) - limited to South America and Central America.
• Ammannia L. (4/25 spp.) - Old world and New World distribution.
• Crenea Aubl. (2/2 spp.) - New World only.
• Cuphea P. Browne (c. 240/c. 240 spp.) - limited to South America, Central America, Mexico, Caribbean, and United States.
• Diplusodon
Pohl (85/85 spp.) - New World only.
• Ginoria Jacq. (13/13 spp.) - present in Greater Antilles and Mexico.
• Heimia Link (3/3 spp.) - limited to South America, Central America, Mexico, Caribbean, and United States.
• Lafoensia Vand. (c. 5/c. 5 sp.) - limited to South America and Central America.
• Lourtella
Graham, Baas, & Tobe (1/1 sp.) - New World only.
• Lythrum L. (2/35 spp.) - Old world and New World distribution.
• Nesaea Comm. (3/c. 50 spp.) - Old world and New World distribution.
• Pehria Sprague (1/1 sp.) - limited to South America and Central America.
• Physocalymma
Pohl (1/1 sp.) - New World only.
• Pleurophora D. Don (c. 6/c. 6 spp.) - New World only.
• Rotala L. (2/44 spp.) - Old world and New World distribution.

Diagnostic

Distinguishing characters (always present)

• No unique synapomorphies.

Other important characters

• Opposite entire leaves.
• Flowers 4-6-merous, but 8-merous in Physocalymma, up to 16-merous in Lafoensia, perigynous, ovarysuperior, infrequently semi-inferior.
• Crinkled petals, often fugacious.
• Stamens 2-whorled (obdiplostemonous), deeply inserted.
• Seeds in most New World genera with inverted trichomes in the epidermal cells of the seed coat that evert on wetting: trichomes spiraled in Cuphea, Lafoensia, Pehria, Pleurophora; trichomes straight in Ammannia, Crenea, Diplusodon, Ginoria, Heimia, Lythrum, Nesaea, Rotala.

Key differences from similar families

• Onagraceae differ from Lythraceae by their viscidpollen threads and, excluding Ludwigia, also by epigynous flowers with inferior ovaries.

Useful tips for generic identification

Key to genera of Neotropical Lythraceae

1. Leaves glandular-punctate, the punctae non-secretory and orange-filled, turning black or secretory and translucent.
1. Leaves non-punctate, glabrous or variously indumented ... 4

2.  Leaves orange to black-punctate, non-secretory; inflorescences multi-flowered clusters ... 3
2.  Leaves translucent-punctate, secretory, blades varnished by resin; inflorescences 3-flowered axillary cymes ...Lourtella

3.  Flowers in compact umbelliform clusters; floral tube campanulate, greenish; capsule indehiscent...Adenaria
3.  Flowers in loose cymose clusters; floral tube cyathiform, deep red; capsule loculicidally dehiscent...Pehria

4.  Floral tubes campanulate to globose or cyathiform, about as long as to slightly longer than wide, actinomorphic... 5
4.  Floral tubes cylindrical, at least twice as long as wide, actinomorphic or zygomorphic... 13

5.  Seeds encircled by a broad, thin wing — 6
5.  Seeds not winged... 8

6.  Floral tubes caducous, distally pleated, (8-)10-12(-16)-merous; leaves with subapical abaxial porate chamber ...Lafoensia
6.  Floral tubes persistent, distally smooth, 6- or 8-merous; leaves normally developed at the apex, lacking a porate chamber ... 7

7.  Trees with strongly divaricate branching; flowers 8-merous; placenta appearing free -central ...Physocalymma
7.  Shrubs and subshrubs with opposite branching; flowers 6-merous; placenta bipartite, septa lunate ...Diplusodon

8.  Trees, shrubs, or subshrubs, 1-40 m ... 9
8.  Annual or perennial herbs, 2 cm - 2m, commonly less than 50 cm ... 1

9.  Stamens basifixed; petals cream-coloured; capsules indehiscent... Crenea
9.  Stamens dorsifixed; petals bright yellow, rose, purple, or white ... 10

10.  Petals bright yellow; flowers solitary; pedicels 0-4 mm ...Heimia
10.  Petals rose, purple, or white; flowers solitary and/or in axillary clusters; pedicels 10-40 mm ...Ginoria

11.  Capsules septicidally dehiscent, wall microscopically (10x) transversely striated; leaves decussate or whorled; leaf base tapered ...Rotala
11.  Capsules splitting irregularly or initially circumscissile, then irregular; wall microscopically smooth, without striations; leaf base auriculate or auriculate... 12

12.  Capsules splitting irregularly; leaf base auriculate...Ammannia
12.  Capsules initially circumscissile, then splitting irregularly; leaf base cordate...Nesaea

13.  Floral tubes actinomorphic;capsules dehiscing from the apex...Lythrum
13.  Floral tubes slightly to strongly zygomorphic, bilateral; capsules indehiscent or dehiscent dorsally by a longitudinal slit together with floral tube ... 14

14.  Stamens attached near base of floral tube, anthers basifixed; capsules indehiscent, placenta and seeds retained within ... Pleurophora
14.  Stamens attached at midlevel or higher in floral tube, anthers dorsifixed; capsules dehiscent dorsally by a longitudinal slit together with floral tube, placenta and seeds exserted...Cuphea

Notable genera and distinguishing features

• Cuphea - largest genus of the family, c. 240 spp.  Endemic to New World.  Unique capsule dehiscence by a longitudinal slit with placenta and seeds emerging for seed dispersal.  Seed oils emphasize lauric acids and diversity of composition includes some with major percentages of caprylic acid.
• Diplusodon - second largest genus of the family, c. 85 spp. Endemic to Brazil and adjacent Bolivia.
• Heimia -  hallucenogenic, anti-inflammatory.

Literature

Important literature

Cavalcanti, T. B.  (in press). Revision of Diplusodon (Lythraceae).  Fl. Neotropica.

Graham, S. A.  1988.  Revision of Cuphea section Heterodon (Lythraceae).  Systematic Botany Monographs. 20: 1-168.

Graham, S. A.  1989.  Revision of Cuphea sect. Leptocalyx (Lythraceae).  Systematic Botany monographs 14: 43-76.

Graham, S. A. 1998.   Revision of Cuphea sect. Diploptychia (Lythraceae). Systematic Botany monographs 53: 1-96.

Graham, S. A.  2010.  Revision of the Caribbean genus Ginoria (Lythraceae), including Haitia from Hispaniola.  Annals of the Missouri Botanical Garden 97: 34-90.

Koehne, E.  1903.  Lythraceae.  326 pp. In: Engler, A. ed., Das Pflanzenreich IV. 216.

Lourteig, A.  1986.  Revision del genero Lafoensia Vandelli (Litraceas).  Mem. soc. ci. Nat. La Salle 45: 115-157.

Lourteig, A.  1986.  Revision del genero Crenea Aublet (Litraceas).  Caldasia 15: 121-142.

Lourteig, A.  1986.  Revision de dos secciones del genera Cuphea P. Browne (Lythraceae).  Phytologia 60: 17-55.

Lourteig, A.  1988.  Revision de Cuphea P. Browne seccion Heteranthus Koehne (Litraceas).  Mutisia 70: 1-20.

M. Thulin et al. Flora of Somalia, Vol. 1-4 [updated 2008] https://plants.jstor.org/collection/FLOS

Morphology General Habit

Herbs (often in or near water), shrubs and trees

Morphology Leaves

Leaves usually opposite, simple, entire; stipules minute or absent

Morphology Reproductive morphology Inflorescences

Inflorescences usually cymose, sometimes congested into raceme-like thyrses

Morphology Reproductive morphology Flowers

Flowers bisexual, usually regular, (3–)4–6(–16)-merous, sometimes heterostylous with individuals differing in the relative lengths of stamens and style

Morphology Reproductive morphology Flowers Calyx

Sepals and petals inserted on a tubular or campanulate “hypanthium” (the “calyx” or “perianth-tube” of some authors); sepals triangular, often with the sinuses between them produced into appendage-like horns

Morphology Reproductive morphology Flowers Corolla

Petals, when present, delicate, often with claw, crumpled in bud, red, pink to purple or white, soon falling

Morphology Reproductive morphology Flowers Androecium Stamens

Stamens usually up to twice as many as sepals, more in some woody genera, inserted on hypanthium, bending inwards; disc absent or very small

Morphology Reproductive morphology Flowers Gynoecium Ovary

Ovary usually superior, (1–)2–6(–8)-celled; placentation axile, rarely basal; ovules 2–many; style simple

Morphology Reproductive morphology Fruits

Fruit usually a capsule, often included within hypanthium

Morphology Reproductive morphology Seeds

Seeds usually small and numerous.

Distribution

About 28 genera and 680 species, mostly in the tropics and subtropics, less numerous in the temperate regions.

Lythraceae, Hutchinson and Dalziel. Flora of West Tropical Africa 1:1. 1954

Morphology General Habit

Herbs, shrubs or trees; leaves opposite or verticillate, rarely alternate; stipules absent or very small

Morphology Reproductive morphology Flowers

Flowers usually actinomorphic, hermaphrodite, solitary to paniculate

Morphology Reproductive morphology Flowers Calyx

Sepals united into a tube, valvate, sometimes with appendages between the lobes

Morphology Reproductive morphology Flowers Corolla

Petals present or absent, inserted towards the top of the calyx-tube, crumpled in the bud

Morphology Reproductive morphology Flowers Androecium

Stamens usually 4 or 8, or rarely more, inserted below the petals; filaments usually inflexed in bud; anthers 2-celled, opening lengthwise

Morphology Reproductive morphology Flowers Gynoecium

Ovary superior, sessile or shortly stipitate, completely or incompletely 2–6-celled (rarely 1-celled); style simple, variable in length; ovules numerous, on an axile placenta sometimes not extending to the top of the ovary

Morphology Reproductive morphology Fruits

Fruit usually capsular, opening by a transverse slit, by valves, or irregularly

Morphology Reproductive morphology Seeds

Seeds numerous, without endosperm; embryo straight

Sonneratiaceae, G. R. Williams Sangai (East African Herbarium). Flora of Tropical East Africa. 1968

Morphology General Habit

Trees or shrubs

Morphology Leaves

Leaves opposite, simple, entire, exstipulate

Morphology Reproductive morphology Flowers

Flowers hermaphrodite, actinomorphic, solitary or 3 together, axillary or terminal

Morphology Reproductive morphology Flowers Calyx

Calyx thick and leathery; tube campanulate; lobes 4–8, valvate

Morphology Reproductive morphology Flowers Corolla

Petals 4–8 or absent

Morphology Reproductive morphology Flowers Androecium

Stamens 12 to numerous, inserted on the calyx, often in several series; filaments free, at length reflexed; anthers reniform or oblong, medifixed, opening lengthwise

Morphology Reproductive morphology Flowers Gynoecium

Ovary free or adnate to the calyx-tube at the base, 4–many-locular; septa thin; ovules numerous, on thick axile placentas, ascending; style long, simple; stigma capitate

Morphology Reproductive morphology Fruits

Fruit a berry or a valvate capsule with 4–many locules and numerous seeds

Morphology Reproductive morphology Seeds

Seeds without endosperm; embryo with short leafy cotyledons

Sonneratiaceae, A. Fernandes. Flora Zambesiaca 4. 1978

Morphology General Habit

Trees or shrubs, with normal and sometimes aerial roots (pneumatophores)

Morphology Leaves

Leaves opposite, petiolate, coriaceous, entire, exstipulate

Morphology Reproductive morphology Flowers

Flowers bisexual, actinomorphic, solitary or in 3s, axillary or terminal

Morphology Reproductive morphology Flowers Calyx

Calyx-tube campanulate, thickly coriaceous, 4–8-lobed, the lobes valvate

Morphology Reproductive morphology Flowers Corolla

Petals 4–8 or 0

Morphology Reproductive morphology Flowers Androecium

Stamens 12 to numerous, inserted on the calyx-tube usually in several series; filaments free; anthers reniform, medifixed, opening longitudinally

Morphology Reproductive morphology Flowers Gynoecium

Ovary free or adnate at the base to the calyx-tube, 4-many-locular; septa thin; style long; stigma subcapitate; ovules numerous, embedded in thick axile placentas, ascending

Morphology Reproductive morphology Fruits

Fruit a many-seeded berry or a capsule

Morphology Reproductive morphology Seeds

Seeds without endosperm; embryo with short leafy cotyledons

Trapaceae, J. P. M. Brenan. Flora of Tropical East Africa. 1953

Morphology General Habit

Aquatic floating herbs

Morphology Leaves

Leaves alternate, floating, rosetted, only present at the upper nodes; stipules small, scarious, cleft to base and thus apparently more than two per leaf; petiole spongy and more or less inflated about the middle; lamina rhombic to deltoid

Morphology Roots

Adventitious roots (?) submerged, paired but not opposite, one from either side of leaf-scar, chlorophyllose and thus leaf-like, pinnatisect into many filiform segments

Morphology Reproductive morphology Flowers

Flowers solitary from upper axils, pedunculate, hermaphrodite, regular

Morphology Reproductive morphology Flowers Calyx

Sepals, petals and stamens 4, latter perigynous

Morphology Reproductive morphology Flowers Corolla

Petals white

Morphology Reproductive morphology Flowers Gynoecium

Ovary half-inferior, bilocular; ovules pendulous, one per loculus

Morphology Reproductive morphology Fruits

Fruit a one-seeded, top-shaped drupe; pericarp soon disappearing; endocarp very hard, variously 2–4-horned, the horns derived from the persistent sepals

Trapaceae, J.P.M.. Brenan. Flora of West Tropical Africa 1:1. 1954

Morphology General Habit

Aquatic floating herbs

Morphology Leaves

Leaves alternate, floating, resetted, only present at the upper nodes; stipules small, scarious, cleft to base and thus apparently more than two per leaf; petiole spongy and more or less inflated about the middle; lamina rhombic to deltoid

Morphology Roots

Adventitious roots (?) submerged, paired but not opposite, one from either side of leaf-scar, chlorophyllose and thus leaf-like, pinnatisect into many filiform segments

Morphology Reproductive morphology Flowers

Flowers solitary from upper axils, pedunculate, hermaphrodite, regular

Morphology Reproductive morphology Flowers Calyx

Sepals, petals and stamens 4, latter perigynous

Morphology Reproductive morphology Flowers Corolla

Petals white

Morphology Reproductive morphology Flowers Gynoecium

Ovary half-inferior, bilocular; ovules pendulous, one per loculus

Morphology Reproductive morphology Fruits

Fruit a one-seeded, top-shaped drupe; pericarp soon disappearing; endocarp very hard, variously 2–4-horned, the horns derived from the persistent sepals

Trapaceae, J. P. M. Brenan. Flora Zambesiaca 4. 1978

Morphology General Habit

Aquatic floating herbs

Morphology Leaves

Leaves alternate, floating, in rosettes, only present at the upper nodes; stipules small, scarious, cleft to base and thus apparently more than two per leaf; petiole spongy and more or less inflated about the middle; lamina rhombic to deltate

Morphology Roots

Adventitious roots (?) submerged, paired but not opposite, one from either side of petiole or leaf-scar, chlorophyllose and thus leaf-like, pinnatisect into many filiform segments; in those from upper nodes segments shorter or absent

Morphology Reproductive morphology Flowers

Flowers solitary, from upper axils, pedunculate, hermaphrodite, regular

Morphology Reproductive morphology Flowers Calyx

Sepals, petals and stamens 4, the latter perigynous

Morphology Reproductive morphology Flowers Corolla

Petals white

Morphology Reproductive morphology Flowers Gynoecium

Ovary half-inferior, bilocular; ovules pendulous, one per loculus

Morphology Reproductive morphology Fruits

Fruit a one-seeded, top-shaped drupe; pericarp soon disappearing; endocarp very hard, variously 2–4-horned, the horns derived from the persistent sepals