Hypericum monanthemum (Nomenclature)
Perennial herb (0.05)0.1-0.4 m tall or long, erect or decumbent to prostrate from creeping, rooting and branching base, with stems scattered or clustered or often carpeting, often slender, unbranched above or rarely with one pair of ascending branches below inflorescence. Stems terete or 2(4)-lined, eglandular; internodes 5-50 mm, longer than leaves. Leaves sessile (uppermost or very rarely all) or to 1 mm petiolate, lower smaller, erect to appressed, soon deciduous; lamina 4-25(-35) ´ 2-15(-25) mm, broadly ovate or circular to broadly oblong or broadly elliptic or obovate-spathulate, paler or slightly glaucous beneath, plane, subchartaceous to submembraneous; apex rounded or retuse to obtuse, margin entire, plane, base rounded to truncate or subcordate or (lower) cuneate; venation 3(4) pairs of main laterals from lower third of midrib, with tertiary reticulation dense; laminar glands punctiform, all pale and very small or some or all black; intramarginal glands black and dense or reddish to pale and rather sparse. Inflorescence 1-5(-7)-flowered, from 1(2) nodes, subumbelliform or bifurcate; pedicels 0.5-2.5 mm (-5 mm in central flower); bracts foliaceous, the pair usually wider than inflorescence, entire; bracteoles narrowly ovate to lanceolate, black-glandular-ciliate and -auriculate, persistent. Flowers (6-)10-25 mm in diam., stellate or reflexed; buds narrowly ovoid, obtuse. Sepals 5, subequal or 4 in unequal pairs, erect in bud and fruit, 2.5-7 ´ 1-3 mm, oblong or elliptic to narrowly ovate or linear-lanceolate, obtuse (rarely acute) to rounded, glandular-ciliate to entire; veins 5-7, branching and often reticulating towards margin; laminar glands all pale or parts or all black, linear; marginal glands black, on cilia or sessile, or reddish to pale, sessile or intramarginal. Petals 5-4, golden yellow, not tinged red in bud, (3-)5-15 ´ 1-4.5 mm, 1-2 ´ sepals, lanceolate-oblong to narrowly ovate, obtuse to acute, margin entire, laminar glands few, pale or black, linear to striiform, or absent, apiculus gland reddish, other marginal glands absent. Stamens 10-45, '3'-fascicled, longest c. 4-9 mm, 0.6-0.8 ´ petals; anther gland black. Ovary (2?)3(4?)-locular 2-5 ´ 1.5-2.5 mm, ovoid to subglobose; styles (2)3(4), 1.5-3.5(-4) mm, 0.5-1 ´ ovary; stigmas narrow. Capsule (5-)6-8 ´ (3-)4-6 mm, broadly ovoid-ellipsoid to ellipsoid; valves with numerous longitudinal vittae. Seeds yellowish-brown, 0.7-0.8 mm, cylindric, acute at both ends; testa shallowly foveolate.
Clearings in forests and bamboo forests, thickets, grassy or stony slopes and streamsides, rock crevices; 2270-4400(-4800) m.
Himalayan Range from W. Sichuan and Yunnan to Nepal.
Joseph Hooker collected two similar plants in Sikkim, one with a 5-merous perianth and the other with a 4-merous perianth. Thistleton Dyer (1874) placed the former in Hypericum (H. monanthemum) and the latter along with other 4-merous Hypericum relatives in the Linnaean genus Ascyrum (A. filicaule), even though all previously described Ascyrum species had been shrubs or herbaceous derivatives from eastern North America and the Caribbean. In addition, A. filicaule has black anther glands, whereas all the American plants are completely destitute of black glands. The Himalayan plant would therefore seem to have developed 4-mery independently.
A detailed study has revealed that not only is A. filicaule a Hypericum, but that it is only with difficulty separable from H. monanthemum. This species displays a western reduction trend, from China to Nepal, while the reduction trend in A. filicaule goes in the reverse direction, from Nepal and Sikkim to Yunnan and Burma. In Nepal, Sikkim and Bhutan there is an area of morphological overlap, where some specimens have perianth states intermediate between 5-mery and 4-mery. It therefore seems appropriate to treat these taxa as subspecies.