3. Triodanis Raf.

Plants annual. Stems erect or loosely ascending, unbranched or less commonly few-branched, mostly from the basal half. Basal leaves usually absent at flowering. Stem leaves sessile or the lowermost leaves less commonly short-petiolate, the margins entire or bluntly to sharply toothed and often inconspicuously hairy. Inflorescences of solitary axillary flowers or small axillary clusters of 2 or 3(–5), mostly very short-stalked, the leaves subtending flowers essentially indistinguishable from the often relatively few foliage leaves, the whole inflorescence appearing spicate. Flowers epigynous, those at the lower nodes cleistogamous (obligately self-fertilizing and probably apogamous), these smaller than the open-flowering ones, the calyx most often with usually only 3 or 4(–6) lobes, the corolla reduced to short flaps of tissue, the stamens variously reduced but when present failing to dehisce or release pollen, and the style highly reduced and nonfunctional. Calyces in normal flowers actinomorphic, (2–)5(6)-lobed, without appendages. Corollas in normal flowers actinomorphic, broadly bell-shaped to saucer-shaped, (3–)5(6)-lobed, the lobes longer than the tube, usually relatively slender (lanceolate to elliptic), blue, purple, or white. Stamens in normal flowers (3–)5(6), attached to the base of the corolla, the filaments short, dilated and hairy at the base, the anthers distinct, elongate. Pistil with 3 carpels. Ovary totally inferior, with 1–3 locules. Style relatively short, straight, the stigma (2)3-lobed. Fruits ellipsoid to narrowly ovoid, narrowly ellipsoid, or narrowly cylindrical capsules, usually with longitudinal nerves, these sometimes minutely ridged toward the tip, dehiscent by 1–3 lateral pores or slits, glabrous or minutely hairy or roughened along the nerves. Seeds ellipsoid, sometimes somewhat flattened, the surface tan to dark brown, shiny (except often in T. perfoliata). Seven or 8 species, North America, Europe, Asia, Africa.

The center of diversity for Triodanis is in the south-central portion of the United States. Only one species (T. falcata (Ten.) McVaugh) occurs in the Old World. All of the species are winter annuals, germinating in the autumn, overwintering as basal rosettes, and flowering the following spring. The regular production of cleistogamous flowers in Triodanis is distinctive but also occurs in a few species of non-Missouri Campanula. The distinction between Triodanis and Specularia Heister ex A. DC., and whether these should be viewed as separate from Campanula, has been somewhat controversial. The species here recognized as Triodanis originally were included in Campanula and subsequently segregated into Specularia. Triodanis was described as a mostly New World segregate of an otherwise Eurasian Specularia. However, the latter name has disappeared from the botanical literature on Old World plants, as it is a nomenclatural synonym of Legousia J.F. Durande. See McVaugh (1945, 1948), Bradley (1968), and Rosatti (1986) for further discussion. The cultivated Venus’ looking-glass, Legousia speculum Fisch. ex A. DC. (Specularia speculum A. DC.), sometimes is grown in Missouri gardens and differs from Triodanis in its more-branched stems, inflorescences in terminal clusters, and lack of cleistogamous flowers.