Hypericum tenuicaule (Nomenclature)
Shrub c. 1-5 m tall, bushy, with branches ascending to arching, not frondose. Stems red, 4-lined when young, soon terete; internodes 8-14 mm, shorter than leaves; bark reddish-brown to grey-brown. Leaves petiolate, with petiole 0-5-2 mm long; lamina 15-58 x 4-19 mm, lanceolate to rarely elliptic, acute to rounded, not or scarcely apiculate, margin plane or rarely undulate, not incrassate, base cuneate to angustate, ± glaucous beneath, chartaceous; venation: 2-3 pairs main laterals, with midrib branched distally, without visible tertiary reticulum; laminar glands streaks and dots; ventral glands dense. Inflorescence l-4(-7)-flowered, from 1(2) node(s), corymbiform, with short (sometimes very short) apical internode, without flowering branches from middle of current stem; pedicels 9-15 mm long; bracts squamiform, acute, deciduous. Flowers 15-30 mm in diam., ± deeply cyathiform; buds subglobose, obtuse to rounded. Sepals 4-5 x 1.8-2.3 mm, free, subimbricate, equal, erect in bud and fruit, oblong to oblong-spathulate, rounded or rarely with minute apiculus, with margin entire or minutely eroded-denticulate (and then hyaline); midrib obscure or indistinct, veins not prominent; laminar glands linear, numerous. Petals bright yellow, sometimes tinged red, ± incurved, 10-13 x 8-12 mm, c. 2-5 x sepals, obovate to subcircular, with apiculus subterminal, rounded or almost absent; margin entire, with or without a few intramarginal or marginal gland dots. Stamen fascicles each with 30-35 stamens, longest 5-7 mm long, c. 0.5 x petals; anthers bright yellow. Ovary 4-5 x 2.5-4 mm, ovoid; styles 3.5-6 mm, 0.9-1.2 x ovary, erect, straight or outcurved very near apex; stigmas small. Capsule 8-11 x 4-7 mm, ± broadly ovoid. Seeds dark brown, 0.7-0.8 mm, cylindric, not carinate, shallowly linear- foveolate.
On 'rocky bank under trees' (Beer, Lancaster & Morris 9493); 1300-3150 m.
Bhutan, Sikkim, Nepal (east).
H. tenuicaule resembles H. williamsii, but differs in its more delicate habit with narrower, not or scarcely apiculate leaves and small flowers on longer pedicels. The areas of these two species overlap in Sikkim only; H. tenuicaule occupies the 'gap' in the distribution of H. williamsii between Sikkim and the Khatmandu region. It seems clear that H. tenuicaule is derived from H. williamsii, or they have had a common ancestor; but even in Sikkim they are apparently always mutually distinguishable. On the other hand, Keith Rushforth, from observations in the field, has suggested to me that they are not distinct. This contradiction is likely to be resolved only by further collecting.
H. tenuicaule has, however, been confused with H. uralum; these sympatric species can always be differentiated by habit, stem-lines, and styles: frondose shoots, 4-lined stems, and styles 0.6-0.9 x ovary in H. uralum; divaricately branched shoots, terete stems, and styles 0.9-1.2 x ovary in H. tenuicaule. The presence of resinous glands on the underside of the leaf in the latter will immediately distinguish this species from H. hookerianum.