Hypericum macvaughii (Nomenclature)
Hyperico formoso Kunth affinis, sed caule 2 lineabus infrafoliaribus irregularibus glandularum nigrarum punctiformium interdum ornato, foliis ellipticis vel oblongo-ellipticis vel oblanceolatis, glandulis laminaribus praecipue nigris vel praecipue pellucidis, floribus minoribus, alabastris haud rubrotinctis, sepalis integris vel subintegris, petalis haud apiculatis, staminibus paucioribus, stylis brevioribus, inter alia differt.
Perennial herb (0.12–)0.3–0.65 m tall, erect, not creeping or rooting at base, usually branching above or at most nodes with branches ascending. Stems very shallowly 2(4)-lined above, soon or wholly terete, occasionally turning vinous red, eglandular or with 2 irregular infrafoliar lines of black punctiform glands; internodes 10–45 mm, exceeding to shorter than leaves. Leaves sessile to subsessile; lamina 12–35 × 2.5–17 mm, elliptic or oblong-elliptic or oblanceolate to linear, paler beneath, chartaceous; apex rounded, margin plane to recurved, base cordate-amplexicaul or usually rounded to narrowly cuneate; venation: 2–3 main laterals from base or near base to lower half of midrib, tertiary reticulation dense, often rather obscure, visible beneath; laminar glands mostly pale with few black distally to mostly black, large, dense; intramarginal glands black, dense. Inflorescence c. 18–numerous-flowered, from 3–4 nodes, ± dense with partial inflorescences also dense, with spreading to ascending branches from up to 13 nodes below, the whole broadly pyramidal to cylindric or corymbiform; pedicels 1–2 mm; upper leaves reduced, bracts and bracteoles 1.5–5 mm, linear to linear-subulate, entire or with some prominent glands. Flowers 12–16 mm in diam., stellate; buds ellipsoid, acute, not red-tinged. Sepals 5, equal, free, 3.5–5 × 0.7–1 mm, lanceolate to linear-lanceolate, acute, entire or with ± prominent glands; veins 5, unbranched; laminar glands black, linear to punctiform, dense to rather few; marginal glands black, few, immersed to sessile or ± prominent. Petals 5, yellow, 6–7.5 × 2–3 mm, 1.5–1.7 × sepals, ± narrowly oblanceolate, rounded; laminar glands black, striiform to punctiform, dense to sparse; marginal glands black, sessile to slightly prominent. Stamens 16–24, ‘3’-fascicled, longest 6–6.5 mm, 0.9–1 × petals; anther gland black Ovary 2 × 1–1.5 mm., ovoid; styles 3, 3–4 mm, 1.5–2 × ovary; stigmas narrowly capitate. Capsule 6–7 × 3–4 mm, narrowly ovoid, longitudinally vittate. Seeds not seen.
Open and dense Pinus-Quercus or Quercus woodland and shaded ravines; 810–3300 m.
Mexico (Chihuahua, Durango, Nuevo Leon, Tamaulipas).
Hypericum macvaughii is closely related to the western form of 6. H. formosum, differing from it in having smaller, narrower leaves with at least some pale laminar glands, a more branched habit and inflorescence (with flowering branches from up to 13 nodes below the main inflorescence), and smaller flowers with only black laminar petal glands. At least one specimen from southwest Chihuahua (Gentry 2546) has some characters tending towards H. formosum: leaves relatively large (to 58 × 20 mm) with laminar glands all black, flowers relatively large (sepals 5 mm long, petals 8 mm long), sepal laminar glands all black, ovary 2 × 1 mm with styles 5–6 mm (2.5–3 × ovary). Other characters, however, are typical of H. macvaughii. The other Chihuahuan specimen cited above (Nelson 4840) I have not seen since working out the specific limits of that species in detail.
Hypericum macvaughii has a bimodal distribution. In the Sierra Madre Occidental it occurs at 1900–2400 m and is, as I have said, morphologically very close to the western form of H. formosum. On the Sierra Madre Oriental the leaves are narrower and usually smaller and the flowers (in the whole inflorescence or partial inflorescences) more crowded, and it occurs at under 1000 m. The Maysilles Durango collection, however, is morphologically nearer the plants from Tamaulipas and Nuevo Leon than it is to the other Durango specimens (i.e. to the type).