Hypericum punctatum
Hypericum ×mitchellianum
spotted St. John's-wort
Blue Ridge St. John's wort
clustered, internodes not lined, with black glands scattered all over.
internodes usually 2-lined, sometimes 4-lined or not lined, with black glands scattered on and near lines or all over.
spreading or ascending, usually sessile, rarely petiolate (to 1 mm);
blade elliptic or oblong to lanceolate or triangular-lanceolate, or oblanceolate, 14–40(–58) × 3–17(–22.5) mm, base cordate to narrowly cuneate, margins plane, apex usually rounded to retuse, rarely acute to obtuse, midrib with 3–5 pairs of branches, tertiary veins densely reticulate toward margins, black glands intramarginal (dense) and laminar (scattered).
spreading, usually sessile, rarely petiolate (to 0.8 mm);
blade ovate-oblong to oblong or elliptic, 30–42(–52) × 8–22 mm, base subcordate to rounded, margins plane, apex usually rounded, rarely obtuse or subretuse, midrib with 4–5 pairs of branches, tertiary veins densely reticulate toward margins, black glands intramarginal (dense) and laminar (scattered).
subcorymbiform to cylindric, 10–206(–600)-flowered, subsidiary branches narrowly ascending to curved-ascending.
corymbiform to broadly pyramidal, (5–)13–61(–124)-flowered, subsidiary branches narrowly ascending or curved-ascending.
8–15 mm diam.;
sepals not imbricate, erect in fruit, lanceolate or oblong-lanceolate to elliptic or ovate-elliptic, subequal, (1.5–)2–4 × 0.8–1.6 mm, apex acute to rounded;
petals pale yellow, oblanceolate to elliptic, 3–6(–9) mm;
stamens (20–)30–60;
anther gland black;
styles 1–4 mm.
15–20 mm diam.;
sepals not imbricate, erect in fruit, lanceolate to ovate-elliptic or elliptic, subequal, (3–)3.6–4.6(–5.5) × 1–2 mm, apex acute to obtuse;
petals golden yellow, narrowly obovate or oblanceolate to elliptic, 6–11 mm;
stamens (37–)42–56(–62);
anther gland black;
styles 1.5–5 mm.
ovoid to subglobose, 2.5–6 × 2–3.5(–4) mm, with longitudinal vittae or elongate to ovoid vesicles.
ellipsoid to subglobose, 3–7 × 3–4.5 mm, with longitudinal vittae.
not carinate, 0.5–0.7 mm;
testa linear-reticulate.
not carinate, 0.7–0.9 mm;
testa not seen.
= 14, 16.
= 16.
Hypericum punctatum
Hypericum ×mitchellianum
Hypericum punctatum has been confused with H. pseudomaculatum; it can almost always be distinguished by style length and anther gland (black in H. punctatum, amber or pellucid in H. pseudomaculatum). D. E. Culwell’s (1970) record of one specimen of the latter from Missouri with a black anther gland could refer to a hybrid; he and other authors agree that such plants are rare, despite the considerable overlap in distribution of these species. Culwell remarked on the unexpected fecundity of the experimentally produced cross H. graveolens × punctatum but nowhere compared the resulting plants with H. ×mitchellianum, a probable hybrid with that parentage (see discussion
under H. ×mitchellianum. Both H. punctatum and H. ×mitchellianum (but not H. graveolens) display a ring of 16 chromosomes at meiosis, and Culwell suggested that this phenomenon may imply some degree of pseudogamy in the group. C. R. Bell (1965) recorded n = 7 chromosomes for this species; his illustration shows n = 8.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Hypericum ×mitchellianum is intermediate in all characters between H. graveolens and H. punctatum and, like the latter, produces a ring of 16 chromosomes at meiosis (D. E. Culwell 1970). Culwell has shown that it hybridizes with H. graveolens in the field and that these species can be crossed artificially. He apparently never suspected that H. mitchellianum could itself be a hybrid. Its intermediate morphology and breeding behavior, together with a distribution almost wholly within that of H. graveolens, suggests strongly that H. mitchellianum is the hybrid H. graveolens × punctatum, which apparently arose when the area of H. punctatum extended into that of H. graveolens.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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