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Published In: Manual of the Botany of the Region of San Francisco Bay 230. 1894. (Man. Bot. San Francisco Bay) Name publication detailView in Biodiversity Heritage Library

Project Name Data (Last Modified On 8/11/2017)
Acceptance : Accepted
Project Data     (Last Modified On 7/9/2009)
Status: Native


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1. Triodanis biflora (Ruíz & Pav.) Greene (small Venus’ looking-glass)

Campanula biflora Ruíz & Pav.

Specularia biflora (Ruíz & Pav.) Fisch. & C.A. Mey

T. perfoliata (L.) Nieuwl. var. biflora (Ruíz & Pav.) T.R. Bradley

Pl. 332 g; Map 1413

Stems 10–40(–50) cm long, erect or nearly so, roughened with minute, recurved hairs along the angles, at least toward the base. Basal leaves elliptic to obovate, tapered to a sessile or short-petiolate base, rounded or bluntly pointed at the tip. Stem leaves 5–20 mm long, 2–10 mm wide, 1.5–3.0 times as long as wide, elliptic to narrowly ovate, sessile but not or only slightly clasping the stem, mostly bluntly pointed at the tip, the margins finely scalloped or bluntly toothed to nearly entire, the upper surface glabrous or nearly so, the undersurface finely roughened or with relatively soft, inconspicuous hairs, mostly along the veins. Flowers 1–3 per node at most nodes of the stem, mostly cleistogamous, the normal open-flowering one(s) usually solitary (rarely 2 or 3) at the stem tip. Calyces with the tube 3–7 mm long, usually appearing slightly inflated, the lobes in normal flowers 5–8 mm long, narrowly triangular to lanceolate, those in cleistogamous flowers 0.7–2.0 mm long, narrowly triangular. Corollas in normal flowers purple to lavender, the lobes 5–9 mm long, 2–3 mm wide. Fruits all similar in size and shape, straight and strongly ascending, 4.5–8.0 mm long, 1.2–2.0 mm wide, the (usually) 3 pores 1.0–1.2 mm long, oval to nearly circular, positioned at or near the tip of the fruit. Seeds 0.4–0.6 mm long, elliptic to broadly oblong-elliptic, slightly flattened (relatively plump), the surface smooth, shiny. 2n=56. May–June.

Scattered mostly south of the Missouri River (southern U.S. north to Oregon, Nebraska, Illinois, and New York). Upland prairies, glades, ledges and tops of bluffs, openings of mesic to dry upland forests, fens, margins of ponds, lakes, and sinkhole ponds, and banks of streams and rivers; also old fields, fallow fields, pastures, ditches, railroads, roadsides, and open, disturbed areas.

This species is closely related to T. perfoliata, and the two species sometimes are found in mixed colonies. The two taxa can be crossed relatively easily (Bradley, 1968, 1975). The hybrids are fertile, robust, and intermediate between the parental forms in most characters, except that the inflorescence always has more than a few open flowers, as in T. perfoliata. Bradley felt that because the two taxa form viable hybrids both in the greenhouse and in nature, they should be considered varieties of a single species. The alternative interpretation was presented by Ward (1978), who noted that most plants can be assigned to one of the parental taxa without difficulty, that several morphological characters correlate to separate the two taxa, and that cleistogamous flowers help to maintain the integrity of each taxon by providing a partial genetic isolating mechanism. For these reasons, the two taxa are maintained as separate species in the present treatment, but users should be aware that a certain proportion of the plants in the complex encountered in the field and herbarium cannot be determined to species with confidence.



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