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Published In: Flora Telluriana 3: 78–79. 1836[1837]. (Fl. Tellur.) Name publication detailView in Biodiversity Heritage Library
 

Project Name Data (Last Modified On 7/9/2009)
Acceptance : Accepted
Project Data     (Last Modified On 7/23/2009)

 

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2. Triadenum Raf. (marsh St. John’s wort)

Plants perennial herbs, with rhizomes, glabrous. Young stems or twigs rounded or slightly angled, not winged. Leaves sessile or short-petiolate, the blades sometimes clasping at the base. Flowers often relatively few, actinomorphic. Calyces of 5 sepals. Corollas of 5 petals, these pink, less commonly flesh-colored, not persistent at fruiting. Stamens 9, in 3 groups of 3, the filaments within a group noticeably fused toward the base. Staminodes 3, alternating with the groups of stamens, appearing as ellipsoid, yellow to orange glandular bodies attached at the base of the ovary. Pistils of 3 fused carpels. Ovary 3-locular, with axile placentation. Styles 3, free to the base, loosely ascending at flowering, the stigmas capitate. Fruits capsules, narrowly oblong-ovoid, 2–3 times as long as the sepals. Seeds numerous, 0.8–1.2 mm long, ovoid-cylindrical, not flattened, rounded to bluntly pointed at the ends, the surface with a network of fine ridges and pits, dark brown. Eight to 10 species, eastern U.S. and Canada, Asia.

Steyermark (1963) and various other earlier botanists treated Triadenum as a section within Hypericum, but Gleason (1947) argued persuasively that the odd staminal characteristics of the species and the petal color warranted the group’s recognition as a separate genus. Subsequent workers (see Wood and Adams, 1976) noted differences in vascular patterns of the flowers and corolla positions in the buds. Thus, most recent authors of floristic manuals (Voss, 1985; Kaul, 1986; Gleason and Cronquist, 1991) have maintained Triadenum as a separate genus.

 

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1 1. Leaf undersurface lacking glandular dots; uppermost leaves of plants at flowering time broadly rounded to cordate at the base (note that this character cannot be evaluated on immature vegetative plants) ... 1. T. TUBULOSUM

Triadenum tubulosum
2 1. Leaf undersurface with clear to light yellowish resinous secretory cavities (visible with magnification), the punctations appearing as pale to nearly clear (rarely darker) glandular dots; leaves all narrowed or tapered at the base ... 2. T. WALTERI Triadenum walteri
 
 
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