Hypericum gymnanthum
Annual herb (0.06-)0.15-0.7 m tall, erect or sometimes with base shortly decumbent and rooting, with stems solitary, without or rarely with l-3(-6) pairs of suberect branches above, with lines smooth; internodes 4-70 mm, long, all or upper exceeding leaves. Leaves sessile, spreading, not tetrastichous, persistent; lamina (5-)10-25 x 3-12 mm, ovate-deltoid or broadly ovate to rarely oblong, plane, not cucullate, midrib prominent beneath, smooth, paler beneath, charta ceous; apex subacute to rounded, margin plane, base cordate-amplexicaul to rounded, not sheathing, free; basal veins (3-)5, often with less prominent ascending midrib branches, tertiary reticulation rather lax, obscure; laminar glands dense, punctiform, not prominent. Inflorescence (l-)5-35(-c. 65)- flowered, terminal, branching regularly dichasial, occasionally with flowering branches from up to 6 nodes below, the whole laxly corymbiform to cylindric; pedicels l-4(-12) mm long; uppermost leaves and bracts subulate, entire. Flowers 4.5-7 mm in diam., stellate. Sepals (3-)3-5.5 x 0.8-1.2 mm, equal, proximally imbricate, lanceolate to narrowly ovate, acute to acuminate, margin entire; veins 3-5, unbranched, not promin ent. Petals golden (?) yellow, not veined red outside, (2-)3-3.5(-4) x 0.9-1.2 mm, shorter than sepals, oblanceolate; apiculus and glands absent. Stamens 10-14, scarcely grouped, longest 1.5-2.5 mm long, c. 0.7 x petals. Ovary c. 1 x 0.5 mm, narrowly ovoid; styles 3, 0.5-0.7 mm long, c. 0.5 (?) x ovary; stigmas narrowly capitate. Capsule (3-) 3.5-5 x 1.5-2 mm, narrowly conic-ellipsoid, slightly shorter than to slightly exceeding sepals. Seeds 0.5-0.6 mm long: testa finely linear-scalariform.
2n = 16 (n = 8: D. H. Webb, 1980).
Bogs, ditches, open and cleared woods, in damp habitats; lowland (U.S.A.), 1300-1400 m (Guatemala).
U.S.A. (eastern Texas to Florida and north to Illinois and Pennsylvania), Guatemala (Alta Verapaz). Introduced into Poland.
H. gymnanthum, H. mutilum and H. boreale together represent a north-eastern disjunct development from 35. H. pauciflorum. H. gymnanthum differs from the Mexico form of that species in its broader, usually ovate-deltoid leaves, the more diffuse inflorescence, and the smaller flowers and fruits. See under42. H. mutilum for the differences from that species.
Both the disjunct areas of H. gymnanthum are likely to have been achieved by long-distance dispersal (as, no doubt, was the original dispersal of 46. H. japonicum to Asia). The Guatemalan population appears to have been first recorded in 1885 and still exists. The Polish population, which was discovered in the same year, was probably introduced with Trifolium seed (Heine, 1962), but apparently did not persist.