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FNA | Family List | FNA Vol. 26 | Orchidaceae

4. Isotria Rafinesque, Med. Repos. hexade 2, 5: 357. 1808.

Whorled pogonia orchid [Greek iso, equal, and tri, 3; probably referring to 3 sepals of equal size and shape]

Loyal A. Mehrhoff & Michael A. Homoya

Herbs, perennial, terrestrial, winter dormant. Roots long, slender, hairy with mycorrhizae. Stems simple, hollow, fleshy, smooth, glaucous. Leaves (2–)5(–6), appearing whorled. Inflorescences terminal; bracts absent. Flowers 1–2, resupinate, erect, yellowish green to white, yellow, and purple, subsessile to pedicellate; sepals of same color, linear-oblanceolate to lanceolate, of equal size; petals oblanceolate, elliptic-obovate, or elliptic-lanceolate, enclosing column; lip apically 3-lobed, lateral lobes triangular, margins involute; callus forming fleshy medial crest; column white, apex denticulate; anther operculate; pollinia 2, hinged, soft, mealy; rostellum obscure; pollen in tetrads, granular; ovary green, slender. Fruits capsules, commonly persistent through following growing season, erect, ellipsoid-cylindric, dehiscent in fall. Seeds 1.2 × 0.2 mm. x = 9.

Species 2 (2 in the flora): e North America.


Ames, O. 1905–1922. Orchidaceae: Illustrations and Studies of the Family Orchidaceae Issuing from the Ames Botanical Laboratory…. 7 vols. Boston and New York. Vol. 7. Homoya, M. A. 1977. The Distribution and Ecology of the Genus Isotria in Illinois. Master’s thesis. Southern Illinois University. Mehrhoff, L. A. 1983. Pollination in the genus Isotria (Orchidaceae). Amer. J. Bot. 70: 1444–1453.

1 Sepals green to light green, less than 30 mm; lip light yellowish green to pale greenish white, streaked with green; pedicel of mature capsule 5–17(–20) mm; stem and leaves pale grayish green.   1 Isotria medeoloides
+ Sepals purplish brown, greater than 30 mm; lip yellowish green to white, streaked with purple; pedicel of mature capsule 20–55 mm; stem purplish to brownish green; leaves green to dark green.   2 Isotria verticillata

Lower Taxa


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