Systematic Treatment of Humiriaceae

Abstract

Small shrubs, treelets or large trees; wood hard, aromatic, often with balsamic sap, heartwood reddish, alburnum yellow or yellowish; bark smooth, striate or fissured. Leaves alternate, simple, distichous, coriaceous or subcoriaceous, penninerved, brochidodromous, from small to large, margins entire, crenulate, dentate or slightly serrate, petiolate or rarely sessile, sometimes decurrent along branches, often punctate-glandulose (nectariferous glands) near margins (or basal) on underside; stipules very small, geminate, often deciduous. Inflorescences (synflorescences) axillary, pseudo terminal or rarely terminal, cymose-paniculate (or thysoid) or often corymbiform, of dichasial type and trichotomous, but through reduction with dichotomous or alternate (cincinnate) branching; branchlets often with incrassate ends, articulate; pedicels short, articulate; bracts and bracteoles persistent or deciduous, small, amplectant. Flowers hermaphroditic, actinomorphic, slightly aromatic; sepals 5, persistent, thick and carnose at base, thinner toward margins, suborbicular or triangular, more or less connate in tube or cupule in varying degrees, glabrous, pubescent or tomentose outside, margins always ciliate, sometimes with marginal or dorsal glands; aestivation quincuncial or imbricate; petals 5, deciduous or sometimes persistent, free, thick or membranaceous, usually 3–5-veined, oblong, linear or oblong-lanceolate, acute to obtuse, 1.5–16 mm long, exceptionally 30–40 mm long, rarely with gland at top, margins smooth, sometimes with tooth at one side near apex, above glabrous, below glabrous or pilose, white, greenish white, or yellowish white, rarely red or purple; aestivation contorted, cochlear or quincuncial; stamens monadelphous, numerous and pluriseriate or of variable number, 1–2-seriate; filaments filiform (when numerous), slender and flexuose, or thick, complanate, linear, acute at apex, straight and glabrous or papillose; connate at base in a more or less long tube, alternating in different lengths, sometimes five alternating with petals are trifurcate at apex and triantheriferous; sometimes with additional staminodial filaments; anthers dorsifixed or subbasifixed; thecae 2, bilocular, laterally attached, ellipsoid-oblong and each cell dehiscing by longitudinal slit, or 4 unilocular, rounded or ellipsoid disjunct thecae (2 lateral and 2 basal), dehiscing by detachment, or two unilocular, disjunct, basal, dehiscing by detachment; connective thick, fleshy, ovoid or lanceolate, obtuse at apex or most commonly produced in apiculum or linguiform appendage; pollen shed as isopolar monads; intrastaminal free disc surrounding ovary, membranaceous or subcoriaceous, nectariferous, annular, tubular or cupular, dentate, lobate, laciniate or composed of 10–20 free scales; style single, entire, columnar, erect, as long as stamens (1.2–12 mm long, exceptionally 30 mm long or shorter (0.3–0.9 mm long), rarely very short and rather thick or longer; stigma narrowly or broadly capitate, 5-lobate or 5-radiate; ovary superior, ovoid or ellipsoid, sessile, syncarpous, (4-)-5(−7) septate with axile placentation, locules uniovulate or biovulate; ovules anatropous, epitropous with 2 integuments, pendant at inner angle of ovary cells, micropyle pointing upward, raphe ventral; when 2 ovules present in each cell, superposite and lower one hanging from longer funiculus. Fruit a drupe (drupoid), from small (not exceeding 16 mm) to large, black, blackish, reddish, yellow, or orange when mature, usually aromatic; exocarp with smooth surface, glabrous, or pilose; mesocarp hard-fleshy varying from pulpy to fibrous, subcoriaceous texture, often aromatic and edible; endocarp woody, usually very hard, compact or with many resin-filled, round cavities, rarely spongy-woody, 5 septate, commonly with only 1–2(−5) seeds developed; surface smooth, bullate, rugose, or tuberculate, slightly striate or strongly costate; with dehiscence germinal, provided with as many longitudinal opercula or valves as carpels, which may open or be pushed away by emerging embryo at germination of seed inside fruit; often subapical foramina present in Duckesia, Endopleura, Humiria, and Humiriastrum. Seeds oblong, with double testa, exterior often adherent to endocarp, inner membranaceous, thin; one or two per locule; embryo straight or slightly curved, cotyledons oblong or ovate, often subcordate at base, radicle half as long, endosperm fleshy and oily.