3. Monotropa L. (Indian pipe, pinesap)

(Wallace, 1995)

Plants perennial mycotrophic herbs, lacking chlorophyll, the entire plant variously white to yellow or red, turning dark brown or black upon drying, glabrous to finely hairy or glandular-hairy. Stems unbranched. Leaves reduced to lanceolate bractlike scales, these shorter and mostly ovate toward the stem base, longer and lanceolate to oblong-elliptic higher on the stem, mostly sharply pointed at the tip. Inflorescences terminal racemes of 3–10 flowers or a solitary terminal flower, nodding during development and at flowering, becoming erect at fruiting. Flowers actinomorphic, perfect, hypogynous, bracteate, stalked. Calyx absent or of 4 or 5 scalelike, free sepals, usually shed as the flower opens. Corollas of 3–6(–8) free petals, broadly tubular or slightly urn-shaped, the petals somewhat pouched at the base, rounded to truncate at the tip. Stamens 6–10, in 2 whorls, not exserted, the outer whorl shorter than the inner whorl, the filaments attached between the pairs of lobes of a prominent nectary disk, usually hairy, the anthers without spurs or appendages, dehiscing by sometimes irregular slits across the tip. Ovary with (4)5(6) locules, superior, the placentation axile. Style 2–3 mm long, stout, straight, enlarging slightly and persistent at fruiting, the stigma obconic or disk-shaped, (4)5-lobed. Fruits capsules, globose to ovoid, the surface with shallow, longitudinal grooves, brown at maturity, dehiscing longitudinally. Seeds numerous, 0.8–1.2 mm long, 0.1–0.2 mm wide, very narrowly ellipsoid, tapered to a tail-like tip at each end, the surface smooth, light brown. Two species, North America to South America, Europe, Asia.

Monotropa and related genera are one of several groups of angiosperms known variously as saprophytes, mycotrophic plants, and epiparasites. In Missouri, the other main group of such organisms occurs in the Orchidaceae. These strange-looking plants have lost their chlorophyll and capacity for photosynthesis, deriving their water and nutrients via soilborne fungi that have established a mycorrhizal relationship with their roots (hence the term mycotrophic). The roots are individually poorly developed and are often clustered into dense, irregularly spherical masses of short roots. The term saprophyte is somewhat misleading, as plants of Monotropa do not, of themselves, derive sustenance directly from decaying organic matter. Instead, the fungal intermediates provide water and nutrients from decay processes and from tree species growing in the vicinity. In experiments involving the injection of radioisotopically labeled substances into the phloem of trees, Björkman (1960) demonstrated the passage of sugars and phosphates from the trees to Monotropa. This has given rise to the designation epiparasite, in recognition of the secondary parasitism of tree species via fungal connections, which is different from the true parasitism of plants such as mistletoes (Phoradendron, Viscaceae) that form direct connections with the vascular system of their hosts.

Species of Monotropa have been used as an eye tonic, sedative, analgesic, and general tonic, among other medicinal uses.