Flora of North America species comparison

frequently creeping and rooting at nodes, procumbent, decumbent, or weakly erect, often branched near base.

erect, decumbent, lax, spreading, creeping, trailing, floating, or submerged, young ones often 4-angled.

opposite;

sessile;

blade spatulate or oblong to broadly obovate or orbiculate, 5–15 × 3–8 mm, base narrowly attenuate.

deciduous, usually opposite, sometimes alternate, subalternate, or whorled, simple, rarely dimorphic, emergent and submerged leaves dissimilar;

stipules usually absent;

sessile, subsessile, or petiolate;

blade membranous [leathery], venation brochidodromous, each marginal vein forming a series of loops, margins entire (except coarsely toothed in Trapa), trichomelike glands present in axil at petiole base.

spikelike.

indeterminate or determinate, terminal or axillary, racemes, spikes, cymes, panicles, [thyrses], or flowers solitary;

bracts absent (except present in Cuphea aspera);

bracteoles present, paired on pedicels.

opposite or alternate, along most of stem, sessile to subsessile, monostylous;

floral tube broadly campanulate, 1 × 1.5 mm;

epicalyx segments equal to or to 2 times longer than sepals;

sepals 1/3–1/2 floral tube length, apex dark red;

petals early caducous, 0 or 6, white to pink or rose, 1 × 0.7 mm;

nectary absent;

stamens 6.

bisexual [unisexual], actinomorphic or zygomorphic;

perianth and androecium usually perigynous (semi-epigynous to epigynous in Punica, perigynous to semi-epigynous in Trapa), mono-, di-, or tristylous;

floral tube or cup persistent, campanulate, turbinate, urceolate, cylindrical, or obconic, green (except red or yellow in some Cuphea and Punica), sometimes conspicuously ribbed;

sepals persistent, 4–8, valvate, usually deltate, sometimes subulate in Lythrum, alternating with segments of epicalyx or epicalyx absent;

petals usually caducous or deciduous, rarely persistent, 0–8, distinct, on interior margin of floral tube between sepals, crinkled, pinnately-veined;

nectary present as distinct organ, as nectariferous tissue in wall of ovary or floral tube, or absent;

stamens (1–)4–42[+], usually equal to or 2 times number of petals, usually in 2 whorls of unequal length, sometimes 1 whorl;

anthers versatile [or basifixed], introrse, 2-locular, longitudinally dehiscent;

pistil 1;

ovary usually superior (semi-inferior to inferior in Punica and Trapa), 2–6-locular (to 9 twisted locules in Punica);

placentation axile, placenta elongate or globose;

septa incomplete near ovary apex (reduced to thin threads in Cuphea);

style 1;

stigma 1, capitate to punctiform, dry (wet in Heimia, Lagerstroemia, and Punica);

ovules 1–1400, anatropous, bitegmic.

capsules, walls usually thin and dry (thick in Decodon, woody in Lagerstroemia), or leathery berries (Punica), or indurated, 2–4-horned drupes (Trapa), usually smooth (striate in Rotala), dehiscence loculicidal, septicidal, or septifragal, or indehiscent and splitting irregularly.

surpassing floral tube, indehiscent, splitting irregularly.

ca. 10–25, subglobose.

3–250(–1400), usually brown (wine in Punica) [black, red], narrowly obovoid to fusiform, oblong to pyramidal, obovoid-semiovoid, semiorbicular, suborbicular, or elliptic (in outline), usually dry, fleshy in Punica, winged or not;

endosperm not developed;

embryo straight, oily, cotyledons usually ± complanate, rarely rolled, often auriculate or cordate.

= 10 (Europe).