CLUSIACEAE (GUTTIFERAE) (St. John’s Wort Family)

Plants annual or perennial herbs or shrubs (trees and lianas elsewhere), sometimes more or less evergreen, sometimes with rhizomes, usually glabrous, the tissues with clear to yellowish to dark green or black resinous secretory cavities, these appearing as dots, lines, or streaks on stems, leaves, and often also floral parts. Leaves opposite, simple, sessile or short-petiolate. Leaf blades simple, the margins entire. Stipules absent. Inflorescences terminal and/or axillary, consisting of clusters of flowers, these often grouped into panicles, sometimes reduced to single flowers, the branch points and flowers often subtended by small, leaflike bracts. Flowers actinomorphic (except in a few Hypericum), perfect, hypogynous. Calyces of 4 or 5 free sepals, usually persistent at fruiting. Corollas of 4 or 5 free petals, these mostly spreading, sometimes withered but persistent at fruiting. Stamens 5 to numerous, often in groups by basal fusion of the filaments, the long, slender filaments occasionally fused to the petal bases, sometimes fused into a short ring around the ovary base, the anthers attached toward the base or more or less medially, yellow or occasionally orange. Staminodes absent (in Hypericum) or glandular (in Triadenum). Pistils of usually 2–5 fused carpels. Ovary superior, with 1–5 locules, with axile (when 2–5-locular) or parietal (when 1-locular) placentation. Styles 1–5, persistent at fruiting, the stigmas capitate or minute. Ovules numerous. Fruits capsules, the body narrowly to broadly ovoid or nearly globose, usually tapered to a stylar beak(s), sometimes appearing somewhat woody at maturity, dehiscing longitudinally. Forty-five to 50 genera, 900–1,350 species, nearly worldwide.

Some authors have treated the group of mostly temperate, herbaceous to shrubby species with perfect flowers, relatively short secretory cavities, glandular-punctate leaves, and seeds lacking arils as a separate family, Hypericaceae, restricting the Clusiaceae to a mostly tropical group of shrubs and trees with usually imperfect flowers, long secretory canals, leaves lacking glandular punctations, and seeds often enclosed in fleshy arils. Studies of comparative anatomy, especially of flower vascular patterns, have offered evidence that the entire set of genera is best treated as a single family (summarized by Wood and Adams, 1976) comprising two or three subfamilies. There is general agreement, however, that Hypericum and Triadenum are closely related and form a natural group within this family.