Flora of North America species comparison

ascending or prostrate, profusely branched basally, radiating from rootstock, mostly 0.2–0.5 m.

without nodal spines (Amaranthus spinosus sometimes with paired nodal spines).

petiole 1/2 as long as to equaling blade;

blade rhombic-ovate or ovate to lanceolate, 1–2 × 0.5–1 cm, base tapering or cuneate, margins entire, plane or slightly undulate, apex subacute, obtuse, or retuse or shallowly emarginate, mucronulate.

alternate or opposite, exstipulate, usually petiolate;

blade margins entire (entire or serrulate in Iresine; entire, crispate, or erose in Amaranthus).

of pistillate flowers linear, 0.5–1 mm, 1/2 as long as tepals.

terminal, erect, compact, pyramidal panicles and also some axillary clusters, green or silvery green, occasionally tinged with red, leafless at least distally.

cymules arranged in spikes, panicles, thyrses, heads, glomerules, clusters, or racemes; each flower subtended by 1 bract and 2 bracteoles (latter sometimes 1 or absent in Amaranthus).

bisexual or unisexual (plants then monoecious or dioecious), hypogynous, generally small or minute;

tepals mostly (1–)4–5 or absent, distinct or connate into cups or tubes, scarious, chartaceous, membranaceous, or indurate;

stamens 2–5, filaments basally connate into cups or tubes, rarely distinct, alternating with pseudostaminodes (appendages on staminal tubes) or not, anthers 2-locular with 1 line of dehiscence or 4-locular with 2 lines of dehiscence;

ovary superior, 1-locular;

ovules 1 or, rarely, 2–many;

style 1 or absent;

stigmas 1–3(–5).

clustered at tips of inflorescences;

tepals 2–3;

stamens 2–3.

tepals 2–3, narrowly elliptic or oblanceolate, not clawed, equal or subequal, 1.2–2 mm, apex broadly acute;

style branches erect;

stigmas 3.

utricles, dry, dehiscent or not.

very dark brown to black, 1–1.2 mm diam., shiny, filling only proximal portion of fruit.

black, reddish brown, or brown, lenticular, subglobose or globose (rarely cylindric), usually small;

embryo peripheral, surrounding mealy perisperm.

marked with 2(–3) green lines that intersect at apex and divide fruit into halves or quarters, slightly to distinctly inflated, ellipsoid, 2–3 mm, distinctly longer than tepals, smooth (in dry plants wrinkled or rugose), indehiscent.