FZ volume:8 part:7 (2005) Avicenniaceae by R. Fernandes
A monogeneric family of the Old and New World tropics and subtropics. Usually treated as a subfamily of the Verbenaceae, it is here recognized as a separate family readily distinguished by the involucre of 1 bract and 2 bracteoles which subtend each flower, the free-central placentation with a c. 4-winged placenta, the orthotropous ovules and by the viviparous embryo and fleshy endosperm. Molecular evidence now places it near the more basal Acanthaceae, with which it shares few essential morphological characters. [A.E. Schwarzbach & L.A. Mc Dade. Phylogenetic relationships of the mangrove family Avicenniaceae based on chloroplast and nuclear chromosomal DNA sequences. Systematic Botany 27: 84–98 (2002)].
Glabrous (or canescent) evergreen small trees of mangrove swamps, with extensive widely-spreading root systems bearing pneumatophores. Leaves simple, decussate, petiolate, without stipules; lamina entire, pulverulent (powdery)-puberulent or felted-tomentellous on lower surface, ± coriaceous. Inflorescences terminal or axillary, of contracted cymes at the end of short peduncles. Flowers actinomorphic, hermaphrodite, sessile, subtended by an involucre formed by a bract and two bracteoles. Calyx gamosepalous, deeply 5-lobed with lobes imbricate. Corolla gamopetalous, campanulate or campanulate-rotate; tube short; limb 4(5)-lobed, spreading, with subequal lobes or the posterior lobe slightly broader. Stamens 4, inserted in the corolla throat and alternating with the lobes, equal or sub-didynamous; filaments ± short, filiform; anthers ovoid or suborbicular, subexserted. Ovary superior, 2-carpellate, but appearing 4-locular due to ovary wall intrusions (false septa); placenta free, axile; style 1 short, bifid or bilobed, with apical stigmas; ovules 4, with 1 in each apparent locule, pendent, orthotropous. Fruit a capsule, l-seeded (by abortion of 3 ovules), usually asymmetric, compressed, opening by 2(4) thickened valves. Seed without a testa; embryo with large longitudinally folded cotyledons and a villous radicle, viviparous; endosperm fleshy.