8. Monotropa Linnaeus, Sp. Pl. 1: 387. 1753; Gen. Pl. ed. 5, 183. 1754.
[Greek monos, one, and tropos, turn or direction, alluding to flowers all turned in one direction on inflorescence axis]
Gary D. Wallace
Herbs, achlorophyllous, heterotrophic. Stems absent. Leaves absent. Inflorescences racemes or solitary flowers, nodding at emergence from soil, becoming erect in fruit, axis fleshy and fibrous, persistent after seed dispersal, white or yellowish to orange or reddish, 0.1-1 cm diam. proximal to proximalmost flower. Pedicels nodding at anthesis, somewhat longer in fruit; bracteoles sometimes present. Flowers radially symmetric, nodding; sepals absent or (3-)4-5(-6), distinct, lanceolate, oblong, spatulate, or elliptic; petals (3-)4-5(-6), distinct, white to pinkish, reddish, yellowish, or orange, without basal tubercles, abaxial surface glabrous, adaxial surface with scattered hairs or hairy, corolla tubular-campanulate; intrastaminal nectary disc present; stamens 8-10(-14), included; filaments ± uniformly slender or slightly broader proximally than distally, glabrous or sparsely hairy; anthers transversely ellipsoid to depressed-ovoid or horseshoe-shaped, without awns, without tubules, dehiscent by 1 slit; pistil (4-)5(-6)-carpellate; ovary (4-)5(-6)-locular; placentation axile; style straight, stout or slender; stigma umbilicate to funnelform, with or without subtending ring of hairs. Fruits capsular, erect, dehiscent basipetally loculicidal, no cobwebby tissue exposed by splitting valves at dehiscence. Seeds 100+, oblong-fusiform, mostly membranously winged. x = 8.
Species 2 (2 in the flora): North America, Mexico, Central America, n South America, Europe, Asia.
Molecular studies have demonstrated the paraphyletic nature of Monotropa and clarified relationships among some of the allied monotypic genera. A treatment realigning several genera of the achlorophyllous heterotrophs is not yet completed. Therefore, Monotropa here includes M. hypopitys and M. uniflora.
Studies by K. W. Cullings (2000) and M. I. Bidartondo and T. D. Bruns (2001, 2002) suggest recognition of potential infraspecific taxa in Monotropa uniflora and M. hypopitys as well as the presence of cryptic species within M. hypopitys.