Hexastylis

Herbs , perennial, evergreen, rhizomatous, without aerial stems. Leaves alternate, 2-ranked; stipules absent; petiolate foliage leaves and sessile, triangular scale-leaves both present. Leaf blade membranous or leathery, glabrous. Inflorescences terminal on rhizome, solitary flowers, subtended by triangular bract. Flowers: sepals connate for most of length, usually mixture of brown, purple, or yellow, externally glabrous, inner surface glabrous, with weak to strong network of ridges, calyx tube never forming differentiated utricle or syrinx; vestigial petals absent; stamens 12, distinct; filaments shorter than pollen sacs; terminal appendage of anther absent or rudimentary; ovary superior or partly inferior, 6-locular; styles 6, distinct (except sometimes at extreme base). Capsule fleshy, dehiscence irregular. Seeds ovoid, not winged, with fleshy appendage. x = 13.

Hexastylis is very similar to the Asiatic genera Heterotropa C. Morren & Decaisne and Asiasarum F. Maekawa; a strong case could be made for combining the three genera. Nevertheless, all three of these genera seem distinct from Asarum (in which they have been included by some authors; e.g., K. Barringer 1993) in their connate sepals, distinct styles, nonappendiculate anthers, and superior or partly inferior ovaries.

Herbarium specimens of Hexastylis are difficult to work with. The form of the calyx is very important taxonomically, but the calyx is fleshy and brittle and does not press well. Allowing flowers to wilt for several hours before pressing may help to reduce distortion, because the calyx becomes more flexible and less likely to split in the press. Features of the inner surface of the calyx are also important, but collectors seldom cut open flowers and press them with the inside visible. For this reason, herbarium specimens of Hexastylis are difficult to identify reliably, and meaningful work on the group requires field studies. L. L. Gaddy (1987) and H. L. Blomquist (1957) gave photographs and drawings of flowers of all species, and an extensive collection of liquid-preserved flowers is housed to the University of Tennessee; these are very helpful in identifying Hexastylis specimens.

Cal regular, tubular, 3-lobed, glabrous outside; pet none; stamens 12, with very short or no filament, appressed to the styles; connective only shortly (if at all) prolonged; ovary superior to half-inferior, 6-locular; styles 6, erect, distinct, each prolonged beyond the conspicuous, extrorse stigma into 1 or 2 erect horns; fr a fleshy capsule, enclosed by the accrescent cal, the two rupturing together at maturity; perennial, evergreen herbs from short or long rhizomes, bearing annually a petiolate, leathery, broadly cordate or hastate, glabrous lf, the old lvs persistent; fls solitary, on a short peduncle from the axil of a bract, greenish or purplish outside, dark red-purple inside; seeds carunculate. Genus often included in Asarum. 4, se. U.S., possibly also some in China.

Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.

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