Hypericum sphaerocarpum
Hypericum densiflorum
round-fruit St. John's-wort, roundseed St. Johnswort
bushy St. John's-wort, dense St. Johnswort
internodes 2–4-lined.
internodes 4-lined at first, soon 2-lined to terete.
blades narrowly elliptic or narrowly oblong to linear, 30–70 × 3–15 mm, base not articulated, narrowly cuneate to linear, margins plane to revolute, apex subacute to rounded, midrib with 0–4 pairs of branches.
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.
rounded-corymbiform, 7–70-flowered, narrowly branched, sometimes with dichasia or branches from to 8 proximal nodes.
broadly pyramidal to broadly cylindric, 5–25-flowered from apical node, with (2–)5–15-flowered dichasia from 1–2 proximal nodes.
10–15 mm diam.;
sepals persistent, not enclosing capsule, 5, broadly ovate to oblong-elliptic, ± unequal, 2.5–5 × 1.5–3 mm;
petals 5, bright yellow, oblanceolate-elliptic to elliptic, 5–9 mm;
stamens persistent, 45–85;
ovary 3-merous, placentation parietal.
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.
broadly ovoid to depressed-globose, 4.5–8 × 4–7 mm.
narrowly ovoid conic to cylindric-ovoid, 5–6(–7) × 2–3 mm, not or scarcely lobed.
carinate, 2–2.7 mm;
testa coarsely reticulate.
not carinate, 0.8–1.3 mm;
testa linear-reticulate.
= 18.
Hypericum sphaerocarpum
Hypericum densiflorum
Hypericum sphaerocarpum differs from H. cistifolium and H. nudiflorum in its semiherbaceous habit and more northwestern distribution, as well as in its combination of relatively long, narrow leaves, persistent sepals, globose and apiculate to rounded capsules, and relatively large seeds. The narrow-leaved, bushy form from eastern parts of the range (var. turgidum) merges with the typical form.
(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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