Corallorhiza

Herbs, perennial, solitary or colonial, mycotrophic, rootless, leafless. Stems erect, yellowish green or brown to purple, glabrous; sheathing bracts few, reduced. Rhizomes branching, coralloid; scales minute. Inflorescences laxly to densely flowered racemes, subtended by 3–4 tubular bracts reduced to closed sheaths, glabrous. Flowers 2–41, inconspicuous to showy; perianth spreading to closed; sepals and petals lanceolate to oblanceolate, apices acute to nearly obtuse; lip broadly obovate, with 2 basal lamellae, often with 2 lateral lobes, narrowed to claw; column curved toward lip, with or without basal auricles; anther incumbent, operculate; pollinia 4, superimposed, yellow, unequal; rostellum triangular; stipe narrowly triangular; ovary narrowly ellipsoid-obovoid, often with small mentum adaxially at distal end. Fruits capsules, pendent, ellipsoid to slightly obovoid, 3-ribbed. Seeds cylindric-fusiform. x = 20, 21.

Distribution

Mostly temperate regions, North America, Central America, 1 circumboreal.

Discussion

Species 11 (7 in the flora).

Sporadically occurring color forms are known in all Corallorhiza species in the flora, and they range from plants with unspotted petals to completely yellow plants, apparently devoid of anthocyanin. Various genera of fungi are known to be associated with Corallorhiza.

Selected References

Freudenstein, J. V. 1997. A monograph of Corallorhiza (Orchidaceae). Harvard Pap. Bot. 1(10): 5–51.

Lower Taxa

Corallorhiza bentleyi, Corallorhiza maculata, Corallorhiza mertensiana, Corallorhiza odontorhiza, Corallorhiza striata, Corallorhiza trifida, Corallorhiza wisteriana

Key

1	Lip with upturned margins giving boat-shaped appearance, especially toward apex; mentum absent; lamellae connate for at least part of length.	> 2
1	Lip without upturned margins, not giving boat-shaped appearance toward apex; mentum present (although sometimes inconspicuous); lamellae distinct.	> 3
2	Callus at base of lip less than 1/3 length of lip; flowers chasmogamous.	Corallorhiza striata
2	Callus at base of lip greater than 1/3 length of lip; flowers cleistogamous.	Corallorhiza bentleyi
3	Lip unlobed; lateral sepals upcurved.	> 4
3	Lip with 2 small lateral lobes or teeth; lateral sepals spreading or downcurved.	> 5
4	Dorsal sepal less than 4.5 mm, 1-veined; flowering Aug–Oct.	Corallorhiza odontorhiza
4	Dorsal sepal greater than 4.5 mm, 3-veined; flowering Jan–Jul.	Corallorhiza wisteriana
5	Sepals 1-veined.	Corallorhiza trifida
5	Sepals 3-veined.	> 6
6	Tip with rounded lateral lobes; mentum obscure, adnate to edge of ovary; dorsal sepal 4.7–15 mm; column 3.3–7.8 mm.	Corallorhiza maculata
6	Tip with acute lateral teeth; mentum prominent, protruding backward along but free from ovary; dorsal sepal 6–12 mm; column 5–8.2 mm.	Corallorhiza mertensiana