13. Obolaria Linnaeus, Sp. Pl. 2: 632. 1753; Gen. Pl. ed. 5, 280. 1754. (as Obularia).
[E]
Pennywort [Greek obolos, coin, and aria, possession, alluding to leaf shape]
James S. Pringle
Herbs perennial, chlorophyllous, glabrous. Leaves cauline, opposite. Inflorescences: flowers terminal and axillary, solitary or in cymules of 3. Flowers 4-merous, subtended by 2 separate, leaflike bracts; calyx absent; corolla white to pale violet, narrowly campanulate, glabrous, lobes imbricate in bud, ascending, slightly longer than tube, entire or erose, with 2 minute scales per petal on proximal part of tube, plicae between lobes absent, spurs absent; stamens inserted in corolla sinuses; anthers distinct, remaining straight; ovary sessile; style persistent, erect, short; stigmas 2, remaining straight; nectaries in ring at base of ovary. Capsules compressed-ovoid, rupturing irregularly. x = 28.
Species 1: c, e United States; temperate areas.
Obolaria has a reduced root system and is probably strongly mycotrophic, although its leaves are green. The paired bracts subtending each flower have often been interpreted as two separate sepals, following T. Holm (1897). As noted by A. Gray (1848b) and as illustrated by Holm, these bracts are sometimes parallel with the carpels with their midveins aligned with the midveins of the carpels, and sometimes at right angles to the carpels, with their midveins aligned with the sutures of the ovary. The case presented by Gray for interpreting these structures as bracts is more convincing.
SELECTED REFERENCES Gillett, J. M. 1959. A revision of Bartonia and Obolaria (Gentianaceae). Rhodora 61: 43–62. Gray, A. 1848b. Obolaria virginica, Linn. Mem. Amer. Acad. Arts, ser. 2, 3: 21–31. Holm, T. 1897. Obolaria virginica L.: A morphological and anatomical study. Ann. Bot. (Oxford) 11: 369–383.
