Hypericum punctatum
Hypericum densiflorum
spotted St. John's-wort
bushy St. John's-wort, dense St. Johnswort
clustered, internodes not lined, with black glands scattered all over.
internodes 4-lined at first, soon 2-lined to terete.
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).
blades narrowly elliptic-oblong or oblanceolate to linear, 20–45 × 2–7 mm, base articulated, narrowly cuneate to attenuate, margins recurved to revolute, apex apiculate-rounded to subacute, midrib with 14–17 pairs of branches.
subcorymbiform to cylindric, 10–206(–600)-flowered, subsidiary branches narrowly ascending to curved-ascending.
broadly pyramidal to broadly cylindric, 5–25-flowered from apical node, with (2–)5–15-flowered dichasia from 1–2 proximal nodes.
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.
10–17(–20) mm diam.;
sepals deciduous, not enclosing capsule, 5, narrowly oblong to oblanceolate-spatulate, unequal or subequal, 4–6 × 1–1.5 mm, basal veins 1–3;
petals 5, deep golden yellow, obovate-oblanceolate, 6–9 mm;
stamens deciduous, 100–150;
ovary 3–4(–5)-merous.
ovoid to subglobose, 2.5–6 × 2–3.5(–4) mm, with longitudinal vittae or elongate to ovoid vesicles.
narrowly ovoid conic to cylindric-ovoid, 5–6(–7) × 2–3 mm, not or scarcely lobed.
not carinate, 0.5–0.7 mm;
testa linear-reticulate.
not carinate, 0.8–1.3 mm;
testa linear-reticulate.
= 14, 16.
= 18.
Hypericum punctatum
Hypericum densiflorum
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.)
Hybrid intermediates between Hypericum densiflorum and H. lobocarpum occur in northwestern Alabama, and a narrow-leaved, small-flowered form in Tennessee and northern Georgia (H. interior) verges toward H. galioides. Hypericum densiflorum is always distinct from H. prolificum in the wild; these species hybridize in gardens. Hypericum ×arnoldianum Rehder, known in cultivation only, was thought by Rehder to have the parentage H. galioides × lobocarpum; on both morphological and cytological grounds, the conclusion of W. P. Adams (1972) that it was H. densiflorum × lobocarpum seems much more likely.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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