Herbs, perennial, terrestrial or aquatic, 1–12.5 dm, from rhizomes. Rhizomes persistent, sympodial, spreading and filiform, or densely clumped, cylindrical, and fleshy. Stems simple, arching or erect. Leaves 2–15, cauline, distichous, clasping or short-petiolate; blade usually ovate, glabrous or weakly pubescent, base rounded or cordiform, margins flat or undulate, denticulate or entire, apex acute or caudate. Inflorescences terminally paniculate or racemose, 5–250-flowered. Flowers 3-merous (6 tepals, 6 stamens) or, by reduction, 2-merous (4 tepals, 4 stamens); perianth spreading; tepals distinct, white, ovate or triangular, equal, 0.5–5 mm; stamens inserted at tepal base; anthers 4-locular, dehiscence introrse; ovary superior, 2–3-carpellate, septal walls with nectariferous canals; style shorter than 1.5 mm; stigma 2–3-lobed, less than 1 mm wide; pedicel subtended by 1 or more bracts. Fruits baccate, variously mottled when immature, bright red at maturity, usually lobed, 4–12 mm wide, pulp thin. Seeds 1–12, globose, 3–6 mm diam.; testa pale brown, thin; endosperm scaly. x = 18.

Distribution

North America, Central America, n Europe, e Asia to the Himalayas.

Discussion

Species 30 (5 in the flora).

Outside the flora area, Maianthemum may be epiphytic, with foliage stems pendent or erect; two species are dioecious; tepals may be fused, the perianth campanulate; and tepals and anthers may be pink, green, or violet.

The two species of Maianthemum that bear 4-tepaled flowers, M. canadense and M. dilatatum, are very similar to one another and to the boreal Eurasian species M. bifolium (Linnaeus) F. W. Schmidt, and the three have sometimes been considered varieties of a single species. In most recent floristic works, the genus Maianthemum has been limited to these three species because of their reduced flowers, whereas the remaining species, which bear 6-tepaled flowers more typical of the Liliaceae, have been placed in the genus Smilacina. J. V. LaFrankie (1986) placed all the species in a single genus.

The monophyly of Maianthemum sensu lato is supported by morphological consistencies including baccate fruits that are marked when immature, a consistent and unique karyotype (S. Kawano and H. H. Iltis 1966; S. Kawano et al. 1967; N. H. Valentine and H. M. Hassan 1971; M. N. Tamura 1995), and molecular analysis (P. J. Rudall et al. 2000; J. Yamashita and M. N. Tamura 2000). The 2-merous floral condition in Maianthemum sensu stricto is the result of anatomical reduction from the 3-merous state (F. H. Utech and S. Kawano 1976).

Selected References

Frankie, J. V. 1984. Anatomy of stem abcission in the genus Smilacina (Liliaceae). J. Arnold Arbor. 65: 563–570.  La

Frankie, J. V. 1986. Transfer of the species of Smilacina Desf. to Maianthemum Wiggers (Liliaceae). Taxon 35: 584–589.  La

Frankie, J. V. 1986b. Morphology and taxonomy of the New World species of Maianthemum (Liliaceae). J. Arnold Arbor. 67: 371–439.

Ihara, M. Suzuki, and H. H. Iltis. 1967. Biosystematic studies on Maianthemum (Liliaceae). I. Somatic chromosome number and morphology. Bot. Mag. (Tokyo) 80: 345–352.

Kawano, S. and H. H. Iltis. 1966. Cytotaxonomy of the genus Smilacina. II. Chromosome morphology and evolutionary consideration of the New World species. Cytologia 31: 12–28.

Kawano, S. and M. Suzuki. 1971. Biosystematic studies on Maianthemum (Liliaceae-Polygonateae [sic]). VI. Variation in gross morphology of M. bifolium and M. canadense with special reference to their taxonomic status. Bot. Mag. (Tokyo) 84: 349–361.    La

Kawano, S., M. Suzuki and S. Kojima. 1971. Biosystematic studies on Maianthemum (Liliaceae-Polygonateae [sic]). V. Variation in gross morphology, karyology and ecology of North American populations of M. dilatatum sensu lato. Bot. Mag. (Tokyo) 84: 299–318.

Takahashi, M. and K. Sohma. 1983. Pollen morphology of the genus Smilacina (Liliaceae). Sci. Rep. Tohoku Imp. Univ., Ser. 4, Biol. 38: 191–218.

Utech, F. H. and S. Kawano. 1976. Biosystematic studies on Maianthemum (Liliaceae). VIII. Floral anatomy of M. dilatatum, M. bifolium, M. canadense. Bot. Mag. (Tokyo) 89: 145–157.

Valentine, D. H. and H. M. Hassan. 1971. Cytotaxonomy of the genus Maianthemum. J. Indian Bot. Soc. 50: 437–446.

Lower Taxa

Maianthemum canadense, Maianthemum dilatatum, Maianthemum racemosum, Maianthemum stellatum, Maianthemum trifolium

Key

1	Rhizomes 8–14 mm wide; inflorescences paniculate, branches well developed; tepals inconspicuous, 0.5–1 mm.	Maianthemum racemosum
1	Rhizomes 1–4.5 mm wide; inflorescences racemose, simple or complex, flowers 1–4 per node; tepals conspicuous, longer than 1 mm.	> 2
2	Rhizomes 15–60 cm × 3–4.5 mm, roots scattered; leaves 8–11 on fertile shoots; tepals 6; immature fruits green striped with black.	Maianthemum stellatum
2	Rhizomes 1–30 cm × 1–2 mm, roots restricted to nodes; leaves 2–4 on fertile shoots; tepals 4 or 6; immature fruits green mottled or spotted with red.	> 3
3	Leaf blade base tapered; racemes simple; tepals 6.	Maianthemum trifolium
3	Leaf blade base with narrow or broad sinus; racemes complex, with 1–4 flowers per node; tepals 4.	> 4
4	Plants 10–25 cm; proximal leaves sessile, blade ovate, base with narrow sinus; distal leaf blade cordate; petiole 1–7 mm; flowers (1–)2(–3) per node.	Maianthemum canadense
4	Plants 20–45 cm; proximal leaves short-petiolate, blade triangular to cordate, base with broad, open sinus; distal leaf blade deeply cordate; petiole 7–10 cm; flowers (1–)3(–4) per node.	Maianthemum dilatatum