Description

Key Characters:

Growth Form: Erect, glabrous perennial herbs, often robust.

Stems: Plants growing from sympodial (unbranched above ground), often tuberous with starchy rhizomes.

Roots: Fibrous root system.

Leaves: Leaves simple. Alternate, 2-ranked. Margins entire. Blades with a prominent midrib and numerous pinnate–parallel lateral veins. Sheathing with a gradual transition into the inconspicuous petiole, petioles without a ligule. Stipules absent.

Flowers: Flowers in inflorescences 1 per aerial shoot, terminal on leafy shoot, pedunculate racemes or panicles of flowers or of 2–flowered monochasial cymes (cincinni); bracts of main axis subtending flowers or cincinni. Flowers bisexual (perfect), conspicuous, irregular, obliquely oriented to the axis, in 2–flowered cymes, these grouped into terminal thyrses or branched thyrses in the axils of the principal bracts. Calyx of 3 sepals; sepals green or purple–tinged, distinct, spirally arranged, similar to one another or slightly dissimilar, persistent in fruit. Corolla of 3 petals, the innermost smaller than the other 2, with the petals, stamens, staminodes, and style adnate to form a short or elongate tube at base. Functional stamen 1, the central member of the inner staminal whorl consisting of a single pollen sac and a petaloid appendage, also with at least 1 petaloid staminode (the labellum), regarded as the outermost element of the inner staminal whorl, labellum always present, curved or rolled outward, usually also with (1)2(–4) additional petaloid staminodes (wings) varying in form and size. Ovary inferior, 3-carpellate, with as many cells, placentation axile; ovules usually numerous per cell, anatropous; style petaloid; stigma papillate, wet.

Fruit: Capsules usually warty; apparently sometimes indehiscent. Seeds with an operculum next to the radicle; not arillate; endosperm starchy; perisperm copious; hard; and starchy.

Ploidy:

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