Hypericum punctatum
Hypericum adpressum
spotted St. John's-wort
creeping St. John's-wort
clustered, internodes not lined, with black glands scattered 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).
subcorymbiform to cylindric, 10–206(–600)-flowered, subsidiary branches narrowly ascending to curved-ascending.
rounded-corymbiform, 13–60-flowered, narrowly branched, without subsidiary branches.
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.
10–15 mm diam.;
sepals persistent, not enclosing capsule, 5, ovate-lanceolate to lanceolate, subequal, (2–)4–7 × 1–1.5 mm;
petals 5, bright yellow, obovate-oblanceolate, 6–8 mm;
stamens persistent, 60–80;
ovary 3-merous, placentation parietal.
ovoid to subglobose, 2.5–6 × 2–3.5(–4) mm, with longitudinal vittae or elongate to ovoid vesicles.
ellipsoid to ovoid-ellipsoid, 3.5–6 × 2–4 mm.
not carinate, 0.5–0.7 mm;
testa linear-reticulate.
slightly carinate, 0.6–0.7 mm;
testa scalariform.
= 14, 16.
= 18.
Hypericum punctatum
Hypericum adpressum
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 adpressum is more herbaceous and rhizomatous than H. sphaerocarpum and has narrower capsules and smaller seeds.
The plants with aerenchymatous tissue in the rhizome (var. spongiosum) are not taxonomically distinct but merely the result of a habitat-induced modification.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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