Venus’ Looking-Glass (Triodanis perfoliata)
A cheerful and distinctive member of the Bellflower family that likes poor soil: this was one of a colony growing out of the gravel by a railroad in Oakmont. Nothing else in our area has the combination of a columnar single stalk with clasping leaves and upward-facing violet-blue flowers. More commonly known in botanical literature under the genus Specularia, which is also called Legousia or Legouzia.
Gray describes the genus (which he calls Specularia) and the species:
SPECULARIA [Heist.] Fabrlcius. VENUS’S LOOKING-GLASS.
Calyx 5 (or 3-4)-lobed. Corolla wheel-shaped, 5-lobed. Stamens 5, separate; the membranaceous hairy filaments shorter than the anthers. Stigmas 3. Capsule prismatic or slender-cylindric, 3-celled, opening by 3 small lateral valves. — Low annuals, with axillary blue or purplish flowers, in American species dimorphous, the earlier small and cleistogamous. (Name from Speculum Veneris, the early name of the common European species.) Legouzia Durand.
S perfoliata (L.) A. DC. Somewhat hairy, 1-9 dm. high; leaves roundish or ovate, clasping by the heart-shaped base, toothed; flowers sessile, solitary or 2-3 together in the axils, only the upper or later ones having a conspicuous and expanding corolla; capsule ellipsoid, short, straight, opening rather below the middle; seeds lenticular. (Legouzia Britton.) —Sterile open ground, s. Me, to Ont., westw. and southw.
In Wild Flowers Worth Knowing, Neltje Blanchan gives us this description:
Venus’ Looking-glass; Clasping Bellflower
Specularia perfoliata (Legouzia perfoliata)
Flowers—Violet blue, from 1/2 to 3/4 in. across; solitary or 2 or 3 together, seated, in axils of upper leaves. Calyx lobes varying from 3 to 5 in earlier and later flowers, acute, rigid; corolla a 5-spoked wheel; 5 stamens; 1 pistil with 3 stigmas. Stem: 6 in. to 2 ft. long, hairy, densely leafy, slender, weak.
Leaves: Round, clasped about stem by heart-shaped base.
Preferred Habitat—Sterile waste places, dry woods.
Distribution—From British Columbia, Oregon, and Mexico, east to Atlantic Ocean.
At the top of a gradually lengthened and apparently overburdened leafy stalk, weakly leaning upon surrounding vegetation, a few perfect blossoms spread their violet wheels, while below them are insignificant earlier flowers, which, although they have never opened, nor reared their heads above the hollows of the little shell-like leaves where they lie secluded, have, nevertheless, been producing seed without imported pollen while their showy sisters slept. But the later blooms, by attracting insects, set cross-fertilized seed to counteract any evil tendencies that might weaken the species if it depended upon self-fertilization only. When the European Venus’ Looking-glass used to be cultivated in gardens here, our grandmothers tell us it was altogether too prolific, crowding out of existence its less fruitful, but more lovely, neighbors.