Fire-flag, arrowroot

Thalia divaricata Chapman; T. trichocalyx Gagnepain; T. welwitschii Ridley

Plants 1--3.5 m. Leaves: basal 2--6, cauline 0--1(--2); sheath green or occasionally red-purple, glabrous; petiole green or occasionally red-purple, glabrous; pulvinus caramel-colored, olive-green, or red-purple, 0.3--2.5 cm, glabrous; blade ovate to narrowly ovate, 19--60 ´ 4--26 cm, firm, stiff-papery, base rounded to subtruncate, apex acute to acuminate, occasionally obtuse with acuminate tip, abaxial surface green, faintly pruinose, glabrous, adaxial surface glabrous. Inflorescences lax, broadly spreading to pendeant, paniclelike array, up to ca. 0.6  1 m; scapes 0.8--2.5 m; rachis not pruinose; internodes 5--20 mm; bracts not pruinose, green or streaked or tinged with purple, narrowly ovate, 1.3--2.8 cm, herbaceous, sparsely to densely villous. Flowers: sepals 0.5--2 mm; outer staminode faint lavender to purple, 15--20 ´ 5--10 mm; callose staminode base yellow, apex purple, apical rim, reflexed, petal-like. Fruits ellipsoid, 9--12 ´ 6--7 mm. Seeds smooth dark brown to black, ellipsoid, 7--10 ´ 5--6 mm. 2n = 18 (Senegal) 2n = 26 (in cultivation).

Flowering summer--fall (late Jun--Dec); fruiting summer--winter (Aug--Jan). Lowlands in ponds, wet roadside ditches, swamps, marshes, cypress sloughs, margin of streams or lakes, full sun, often in regions with pronounced dry season; Fla., La.; Mexico; West Indies; Central America; South America (to Argentina and Paraguay); w Africa.

This species has the widest distribution known for any of the Marantaceae, occurring in both Africa and the Americas. Because of the marked lack of variation among the African populations, it is believed that its occurrence in west Africa was a historically recent, probably accidental, introduction (L. Andersson 1981b). The variation in pubescence and bract size within the American continent has been used as the basis for describing additional species or varieties (L. Andersson 1981b). Populations of Thalia geniculata with a striking red-purple coloration on the petiole, sheath, and pulvinus were described as T. geniculata f. rheumoides Shuey (A. G. Shuey 1975) . Such homogeneous populations are to be expected in a mainly selfing species.

SELECTED REFERENCE

Classen-Bockhoff, R. 1991. Untersuchungen zur Konstruktion des Bestäubungsapparates Von Thalia geniculata (Marantaceen). Bot. Acta 104: 183--193. Kirchoff, B. K. 1986. Inflorescence structure and development in the Zingiberales: Thalia geniculata (Marantaceae). Canad. J. Bot. 64: 859--864.