Hypericum majus
Hypericum scouleri
greater Canada St. John's-wort, greater Canadian St. John's-wort, large Canadian St. John's-wort, large St. John's wort, millepertuis majeur
Norton's St. John's-wort, Scouler's St. John's-wort, western john's-wort, western St. John's-wort
internodes 4-angled.
internodes usually weakly 2-lined, sometimes not lined, without black glands, rarely with reddish glands.
spreading, sessile or distal subamplexicaul;
blade lanceolate to narrowly oblong-elliptic or (proximal) oblanceolate, 10–45 × (2–)6–12 mm, papery to membranous, margins plane, apex acute to rounded, basal or near-basal veins (3–)5–7, midrib with to 4 pairs of branches.
usually spreading, rarely erect, sessile or (proximal) subpetiolate;
blade oblong-elliptic or elliptic to triangular-ovate or (proximal) obovate, 12–28(–32) × 6–15(–18) mm, base subcordate to rounded or (proximal) cuneate, margins plane, apex obtuse to rounded, midrib with 4–5 pairs of branches, tertiary veins not densely reticulate, black glands intramarginal (± dense) and, rarely, (1–2) laminar (distal).
corymbiform to cylindric, 3–30-flowered, usually compact, branching mostly dichasial.
cylindric to narrowly pyramidal, (1–)8–20-flowered.
6–7 mm diam.;
sepals lanceolate to narrowly elliptic, equal, 3.5–6.5 × 0.8–1.5 mm, margins sometimes ciliate, not setulose-ciliate, apex acute;
petals golden yellow, sometimes red-veined, oblanceolate, 3.5–6 mm;
stamens 12–21, obscurely 5-fascicled;
styles 0.6–1 mm;
stigmas broadly capitate.
6–15(–25) mm diam.;
sepals not or scarcely imbricate, erect in fruit, ovate to lanceolate or narrowly oblong, unequal to subequal, 2.5–5.5 × 1–2 mm, apex acute to rounded;
petals golden yellow, sometimes red-tinged, oblanceolate, 7–12 mm;
stamens 50–90(–109);
anther gland black;
styles 2–8 mm.
narrowly conic-ellipsoid, 4–8 × 2.5–3.5 mm, broadest proximal to middle.
oblanceoloid, 6–10 × 3.5–6 mm, with longitudinal vittae.
0.5–0.7 mm;
testa finely linear-scalariform.
not carinate, (0.5–)0.7–0.8 mm;
testa linear-reticulate.
= 16.
= 16.
Hypericum majus
Hypericum scouleri
Hypericum majus was the western member of a vicariant species pair, differing from the originally eastern member (H. canadense) by the broader leaves, usually more-congested inflorescence, and larger flowers. These species became sympatric in glaciated northeastern North America and now hybridize freely, notably in Wisconsin (F. H. Utech and H. H. Iltis 1970). Hybrids are intermediate in form between the parents and have also been recorded from Connecticut, Massachusetts, and New Hampshire. Hypericum majus hybridizes also with H. mutilum, with subsp. mutilum in Maine, and with subsp. boreale in Michigan and Wisconsin.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Some authors have included Hypericum scouleri in central Mexican H. formosum Kunth as a synonym, subspecies, or variety; the similarities in sepal form and glandularity between these species are due to convergence. Hypericum formosum is related to another Mexican species (H. oaxacanum R. Keller); the affinities of H. scouleri are with the H. attenuatum group from eastern Asia. Hypericum scouleri itself does occur in northern and central Mexico as far south as Michoacán, México, and Hidalgo, where it is known by the synonym H. simulans Rose.
J. M. Gillett and N. K. B. Robson (1981) treated the dwarf alpine form of Hypericum scouleri as subsp. nortoniae. Further work has revealed a range of intermediate forms between the two putative subspecies, which prevents their recognition. Likewise, the differentiation of a southern population (H. formosum subsp. formosum in the sense of C. L. Hitchcock) from a northern one [H. formosum subsp. scouleri (Hooker) C. L. Hitchcock] based on the broader, blunter, and less-glandular sepals in the latter, does not appear warranted.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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