Hypopithis Rafinesque (1808); Hypopitys Hill (1756); Monotropion Saint-Lager.

Herbs perennial, mycoparasitic, lacking chlorophyll. Axis nodding, white to reddish. Leaves absent or reduced to laminar structures. Inflorescence scapose or racemose arising from persistent root system. Flowers solitary or in several-flowered racemes, often nodding at anthesis, usually erect in fruit, bracteate. Sepals 4 or 5, usually appressed to petals. Petals 3–6, oblong, often saccate at base, apex dilated. Stamens 8–12 in two series of alternating unequal lengths; anthers horizontally reniform, with terminal slit. Disk of 8–10 distended paired lobes adnate to base of ovary. Ovary (3–)5(or 6)-loculed, with axile placentation; style base sharply differentiated from ovary. Capsules globose to narrowly ovoid, loculicidally dehiscent, valves with marginal fibers; perianth segments early deciduous at fruiting. Seeds many, fusiform, minute; testa thin, prolonged at both ends, minutely reticulate. n = 16, 24.

One of us (Wallace) notes that several taxa included here in synonymy under species of Monotropa and Monotropastrum are ambiguous minor variants in numbers of flowers per raceme and degree of pubescence. Numbers of perianth parts often differ among flowers in the same inflorescence or clump. “Features such as color, number of perianth segments, degree of pubescence, numbers of flowers per axis in multiflowered taxa, and floral sizes were found to be extremely variable even among inflorescences from a single root cluster” (Wallace, Taxon 36: 128–130. 1987).

Two species: cool to temperate regions of the N hemisphere, extending to N South America; two species in China.

(Authors: Qin Haining (覃海宁); Gary D. Wallace)