Hypericum gracillimum (Nomenclature)
Perennial herb 0.15–0.6 m tall, erect to ascending from branching and rooting base, with stems caespitose or few, unbranched below inflorescence. Stems slightly 2(4)-lined to terete, eglandular or, very rarely, with a few black dots; internodes 10–40 mm, shorter to longer than leaves. Leaves sessile to subsessile or rarely to 0.5 mm petiolate, lower or almost all ascending; lamina 15–50 × 7–18 mm, lanceolate to oblong or rather broadly to narrowly elliptic or rarely oblanceolate, paler beneath, chartaceous; apex obtuse to rounded, margin plane, base rounded to broadly cuneate; venation: 3 pairs of main laterals from lower third to 2/5 of midrib, tertiary reticulation rather dense, obscure; laminar glands all black to mostly pale, punctiform, small, dense to rather sparse; intramarginal glands black and often pale, ± dense. Inflorescence 1–9(–14)-flowered, from 1–3 nodes, rarely with branches from up to 3 nodes below, the whole corymbiform to narrowly cylindric; pedicels 1.5–4 mm; bracts reduced-foliar; bracteoles narrowly oblong to linear. Flowers 12–16 mm in diam, stellate; buds ellipsoid, obtuse. Sepals 5, free, subequal to unequal, 3–4.5 × 0.8–1.3 mm, narrowly elliptic to narrowly oblong or linear, rounded to subacute, entire or very rarely with one prominent gland; veins 5, outer branching and anastomosing; laminar glands black, striiform (towards base) to punctiform or all ± punctiform or linear and then all or proximal pale; (intra)marginal glands black, few, distal or usually absent. Petals 5, yellow, not tinged red in bud, 7–9 × 2–4 mm, 2–3 × sepals, obovate, rounded, entire; laminar glands black, interrupted-linear to punctiform; marginal glands black, irregular and distal, or absent. Stamens c. 25–40, longest 6–8 mm, 0.85–0.9 × petals; anther gland black. Ovary 2–3.2 × 1.2–1.5 mm, ± narrowly ovoid to narrowly elliptic; styles 3, free, divergent, 2.5–5 mm, 1.2–1.8 × ovary; stigmas narrowly capitate. Capsule 5.5–9 × 2–4 mm, 1.7–1.8 × sepals, narrowly ovoid to subcylindric. Seeds yellow-brown, 0.6 mm; testa shallowly linear-foveolate.
Japan (central and N. Honshū).
Hypericum gracillimum is clearly related to 33b. H. ovalifolium subsp. ovalifolium, from which it differs by its usually oblong to elliptic and smaller (or at least narrower) leaves, sepals and petals with more punctiform and fewer linear laminar glands and narrow capsules. Kimura (1938) included the type specimen (from Mt. Azumasan, pref. Yamagata) in H. subalpinum as var. longistylum, and later (Kimura, 1951) moved it to H. erectum var. longistylum, which he distinguished from his H. erectum var. subalpinum (= H. subalpinum var. typicum) by the longer styles and wholly black laminar leaf glands. The paratype (from Mt. Myokosan, pref. Niigata) he identified as H. vulcanicum. Neither of these specimens has the row of marginal black sepal glands typical of H. erectum or the slender pedicels and very narrow sepals characteristic of H. vulcanicum. According to Koidzumi's description, however, the characters of his species do agree with those of Kimura's H. subalpinum. This is a good species, varying in style length and type of laminar leaf gland; but it is related to H. ovalifolium, not to H. erectum or H. vulcanicum. Hypericum gracillimum appears to be its correct name.
For a possible occurrence of this species in Kyūshū, see note under H. oliganthum var. nigrum (p. 40).
The Baker and Uno specimens have slender decumbent stems, smaller leaves and shorter styles than usual, but their other characters place them in H. gracillimum. There is also a northward reduction trend in overall size of plant and in leaf width, so that the Iwate populations are considerably smaller in stature and with smaller flowers and narrower leaves than those from Nagano.