Triadenum
Triadenum virginicum
marsh, marsh St. John's wort
marsh St. John's wort, millepertuis de virginie, Virginia marsh-St. John's-wort
internodes with 2 or 4 raised lines at first, then terete (not lined).
internodes 4-lined or 4-angled at first, then terete.
sessile, subsessile, or petiolate;
blade relatively broad, venation pinnate, tertiary veins densely reticulate, glands punctiform, pale (records of black gland dots are probably all due to fungal attack), intramarginal and laminar.
sessile, sometimes amplexicaul;
blade usually ovate or triangular-ovate to elliptic or oblong, rarely oblanceolate, 20–65 × 10–22(–30) mm, base shallowly cordate, apex usually rounded, rarely obtuse to retuse, gland dots laminar (relatively dense, large) and intramarginal (relatively small).
terminal, sometimes also axillary, cymose, 2–15-flowered, or solitary flower, branching dichasial;
bracts and bracteoles relatively small.
laxly cylindric to pyramidal, 3–15-flowered from terminal node, sometimes with subsidiary inflorescences from to 4 proximal nodes and flowering branches from to 6 further nodes.
tubular or campanulate at first, expanding to stellate for short time each day;
sepals persistent, 5, distinct or almost so, margins not glandular-ciliate;
petals deciduous, 5, partly imbricate or contorted, pink or flesh-colored, sometimes green-tinged;
stamens persistent, 9, in 3 fascicles, each with 3 stamens;
filaments of each fascicle 1/5–1/2+ connate;
anthers yellow, isodiametric to oblate or shortly oblong, with amber gland on connective;
staminode fascicles 3, alternating with stamen fascicles;
ovary 3-merous;
placentation axile;
ovules relatively numerous on each placenta;
styles distinct, spreading.
10–15 mm diam.;
sepals oblong to elliptic-oblong or oblong-lanceolate, 4–7(–8) × 1–2 mm, apex acute to acuminate;
petals oblong-elliptic to oblanceolate, 6–9(–10) mm;
stamen fascicles 4–6.5 mm;
filaments 1/5 connate;
styles 2–3.5 mm.
3-valved, with glandular vittae.
cylindric to ellipsoid or ovoid-ellipsoid, (8–)9–10(–12) × 4–5 mm, apex acute.
narrowly cylindric, carinate;
testa reticulate-foveolate.
0.5–1.2 mm.
= 19.
= 38.
Triadenum
Triadenum virginicum
Nomenclatural complexities and confusions associated with Triadenum were reviewed by N. K. B. Robson (1977). B. R. Ruhfel et al. (2011) concluded from molecular studies that Triadenum is part of Hypericum. Robson (2012) gave reasons why Triadenum is generically distinct.
Species 6 (4 in the flora).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Triadenum virginicum is the most widely distributed North American species of Triadenum. In the southwestern part of its range, the leaves are longer and narrower, approaching those of T. tubulosum and T. walteri; it is nearly always distinguishable from the northern T. fraseri by the sepals and styles (see key).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
1. Leaves petiolate. | T. walteri |
1. Leaves sessile or (distal) subsessile | → 2 |
2. Leaves: gland dots intramarginal. | T. tubulosum |
2. Leaves: gland dots laminar and intramarginal | → 3 |
3. Sepals 4–7(–8) mm, apex acute to acuminate; styles 2–3.5 mm. | T. virginicum |
3. Sepals 2.5–5 mm, apex usually obtuse to rounded, rarely acute; styles 0.5–1.5 mm. | T. fraseri |
WA
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