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Herbs slender, erect to prostrate and rooting at nodes, or shrubs or rarely small trees; underwater parts often swollen and spongy or with inflated white spongy pneumatophores. Leaves alternate [or opposite], usually entire; stipules present, reduced and/or deciduous; bracteoles 2, at or near base of ovary, or absent. Flowers perfect, actinomorphic, in upper leaf axils or in spikes, racemes, or clusters; floral tube not prolonged beyond ovary. Sepals (3 or)4 or 5(-7), green, persistent after anthesis. Petals as many as sepals or absent, yellow or white, caducous. Stamens as many as or 2 × as many as sepals; anthers versatile or sometimes basifixed; pollen shed singly or in tetrads or polyads. Ovary with as many locules as sepals, rarely more, apex flat or conic, often with a depressed nectary surrounding base of each epipetalous stamen; stigma capitate or hemispheric, entire or lobed, upper 1/2-2/3 receptive. Fruit an obovoid to cylindric capsule, dehiscent irregularly or by a terminal pore or by flaps separating from valvelike apex. Seeds numerous, in one to several rows per locule, free or embedded in powdery or woody endocarp, raphe small or conspicuous, sometimes equal in size to body of seed. 2n = 16, 32, 48, 64, 80, 96, 128.
Mostly perennial herbs with opposite or alternate leaves and solitary axillary flowers or, by reduction of upper leaves, terminal spikes or heads. Flowers normally 4-merous, the stamens as many as the sepals and with relatively short filaments. Petals often small or wanting; if conspicuous, usually early deciduous. Floral tube not prolonged beyond the ovary. Bracteoles lacking to quite well developed. Sepals persistent; summit of ovary truncate or flattish, or crowned with pyramidal to depressed persistent 4-lobed base of style (stylopodium); style short; stigma capitate to somewhat 4-lobed. Capsule subspheric to obpyramidal, elongate, angled or subterete, dehiscing by a terminal pore or longitudinally. Seeds many, naked with evident raphe and multiseriate in each cell, or rarely enclosed in endo-carp and uniseriate.
Fls 4– or 5(–7)-merous; hypanthium not prolonged beyond the summit of the ovary; sep persistent; pet yellow (in our spp.) or white, soon deciduous, or often wanting; stamens as many or twice as many as the sep; ovary cylindric to obconic or prismatic, often angled or winged; style short, with capitate or lobed stigma; ovules numerous; capsule dehiscent longitudinally or by a terminal pore; seeds when pluriseriate in each locule naked and with an evident raphe, when uniseriate surrounded by endocarp from which they may be separated easily or only with difficulty; herbs (ours) or shrubs, mostly of wet places (sometimes aquatic), with alternate or opposite lvs and small or medium-sized diurnal fls sessile or short-pedicellate in the upper axils (in ours) or in terminal spikes or heads. (Jussiaea) 75, mainly trop. Amer.
Shrub or herb, erect or spreading and rooting at nodes, often aquatic with submerged parts spongy or bearing spongy pneumatophores. Leaves alternate or opposite, rarely whorled, usually entire. Flowers usually solitary, occasionally clustered in upper leaf axils or in an inflorescence, 3–7-merous, usually 4–5-merous, often bracteolate. Hypanthium not prolonged beyond ovary. Sepals 3–7, persistent. Petals as many as sepals or absent, usually 4 or 5, yellow or white. Stamens as many as or twice as many as sepals or occasionally intermediate in number. Ovary with locules usually equal in number to sepals. Fruit an irregularly dehiscent capsule; seeds free or embedded in the endocarp.
Slender-stemmed perennial herbs, less commonly erect shrubs. Underwater parts often swollen, spongy or bearing inflated pneumatophores. Lvs alternate or opposite, simple, mostly entire. Fls axillary, actinomorphic, solitary or clustered in spikes or heads. Floral tube not prolonged beyond ovary. Sepals 3-7, ± persistent at fruiting. Petals as many as sepals or 0, yellow or white. Stamens as many or twice as many as sepals; anthers usually versatile. Stigma entire or 4-lobed; ovary cells 4. Capsule variously shaped, dehiscent by terminal pores or longitudinal flaps. Seeds numerous, small, free or embedded in the woody endocarp.
The reasons for uniting Ludwigia, Jussiaea and Isnardia are reviewed in Reinwardtia 6: 327–427 (1963).
