Hypericum xhyugamontanum (Nomenclature)
Perennial herb 0.05–0.3 m tall, erect to ascending, with stems caespitose, simple or branched. Stems obscurely 2-lined, eglandular; internodes 9–13 mm, shorter than leaves. Leaves sessile; lamina 8–40 × 3–13 mm, oblanceolate to linear-oblanceolate, paler beneath, thinly chartaceous; apex rounded to obtuse, margin plane, base slightly attenuate; venation: 3 pairs of laterals, from lower quarter to 2/5 of midrib, tertiary reticulation lax, obscure?; laminar glands pale, punctiform, dense; intramarginal glands black, irregular. Inflorescence 3-10-flowered, from 2 nodes, without branches below, subcorymbiform; pedicels 3.5–4 mm; bracts and bracteoles foliar, lanceolate to narrowly elliptic. Flowers 7–13 mm in diam., concave?; buds ellipsoid, rounded? Sepals 5, unequal, c. 3–4 × 1–1.6 mm, oblong to ovate-oblong, rounded to obtuse, with c. 3–6 glandular cilia on at least 2/3 of sepals on a plant; veins 5, unbranched; laminar glands pale, linear; marginal glands black, on cilia or sometimes sessile. Petals 5, mid? yellow, not tinged red, 6–8 × 3 mm, 2–2.2 × sepals, oblong-oblanceolate, with prominent glands; laminar glands pale, linear to striiform; marginal glands black, prominent. Stamens 25–50, ‘3’-fascicled, longest 7–8 mm, slightly shorter than petals; anther gland black. Ovary c. 3 × 1.2 mm, ovoid-cylindric; styles 3, free, divergent, 1.3–3 mm, 0.5–1 × ovary; stigmas narrow? Capsule 4.5–7.5 × 2.7–4.5 mm (l : b = 1.4–2.2), 1.5–1.85 × sepals, ovoid-conic. Seeds not described.
2n = 32 (Kato, 1987).
Disturbed habitats.
Japan (Kyūshū-northern and central).
According to Kato (1986a), the parents of this hybrid grow in different habitats (H. kiusianum in comparatively sunny dry places and H. pseudopetiolatum in shaded wet ones) and thus rarely hybridise. In Kyūshū, however, habitat disturbance has often resulted in their growing in close proximity and hybridising. The hybrids (H. ×hyugamontanum) are partially fertile, which results in back-crossing and introgression.