Neotropical Humiriaceae

Luiz Carlos da Silva Giordano

Jardim Botânico do Rio de Janeiro, Rio de Janeiro, Brazil. 

Description

Small shrubs or treelets to 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, 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 hermaphrodite, complete, 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, glabrous, pubescent or tomentous outside, margins always ciliate, sometimes with marginal or dorsal glands; aestivation quincuncial or imbricated: petals 5, deciduous or sometimes persistent, free, thick or membranaceus, 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 in definite 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 +/- long tube, alternating in different lengths, sometimes 5 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 2 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; radially symmetrical, angulaperturate, (2)-3-(4)-zonocolporate, suboblade to subprolate; exine thick, with conspicuous thickenings parallel to the colpi; columellar infratectum sometimes very thin in 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, cells uniovulate or biovulate; ovules anatropous, epitropous with 2 integuments, pending 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 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 spongious-woody, 5 septate, commonly with only 1-2 (rarely 3, 4, or 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. Seeds oblong with double testa, exterior often adherent to endocarp, inner membranaceous, thin; embryo straight or slightly curved, cotyledons oblong or ovate, often subcordate at base, radicle half as long, endosperm fleshy and oily.

Notes on delimitation

  • Recent phylogenetic studies have shown that the order Malpighiales is monophyletic only with the composition of the APG II system (2003), which includes Humiriaceae in this order. Hutchinson, 1926, also included the Humiriaceae in the order Malpighiales; Engler, 1964, included Humiriaceae in the Linaceae in the Geraniales; Cronquist, 1988, placed Humiriacea as an independent family in the Linales.
  • Most authors agree that the Linaceae and Erythoxylaceae are close to the Humiriaceae; likewise Ixonanthaceae and, sometimes, Hugoniaceae. In the APG II system the Hugoniaceae is included in the Linaceae.

Distribution in the Neotropics

  • Duckesia Cuatrec. - Brazil (North).
  • Endopleura Cuatrec. - Brazil (North).
  • Humiria Aubl. - Colombia, Venezuela, Guiana, Surinam, French Guiana, Peru, Brazil.
  • Humiriastrum Cuatrec. - Costa Rica, Panama, Colombia, Venezuela, Guiana, French Guiana, Ecuador,  Peru, Brazil, Bolivia.
  • Hylocarpa Cuatrec. - Brazil (North).
  • Sacoglottis Mart. - Costa Rica, Trinidad, St. Vincent, Panama, Colombia, Venezuela, Guiana, Surinam, French Guiana, Brazil.
  • Schistostemon Cuatrec. - Venezuela, Guiana, Surinam, French Guiana, Peru, Brazil.
  • Vantanea Aubl. - Costa Rica, Panama, Colombia, Venezuela, Guiana, French Guiana, Peru, Brazil, Bolivia.

Distinguishing characters (always present)

  • Wood hard and aromatic, heartwood reddish, alburnum yellow or yellowish.
  • Leaves alternate, simple, distichous, coriaceous or subcoriaceous, penninerved.
  • Stipules very small, geminate. Inflorescences cymose, dichasial type with reductions. Pedicels short and articulate.
  • Flowers hermaphroditic, complete, actinomorphic, slightly aromatic; sepals 5, persistent, more or less connate in tube or cupule, margins ciliate; petals 5, free; stamens 10-200, monadelphous, from 1-2-seriate to pluriseriate; connective of anthers extended. Intrastaminal free disk girdling ovary, annular, tubular or cupular, dentate, lobate, laciniate or composed of 10-20 free scales; ovary superior, syncarpous, (4-) 5 (-7) septate with axile placentation, cells uniovulate or biovulate; ovules anatropous; style single, entire, short or long.
  • Fruits drupoid, from small (not exceeding 16 mm) to large; endocarp woody, compact or with many resin-filled, round cavities, commonly with only 1-2 (rarely 3, 4, or 5) seeds developed; 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 are present.
  • Seeds oblong with double testa; endosperm fleshy and oily.

Other important characters

  • Wood with balsamic sap.
  • Leaves with punctate-nectariferous glands near margins (or basal) on underside.
  • Inflorescences paniculate or often corymbiform.
  • Petals 1.5-16 mm long (white, greenish-white or yellowish-white), exceptionally 30-40 mm long (red or purple).
  • Anthers with 2 bilocular thecae laterally attached, or 4 unilocular disjunct thecae (2 lateral and 2 basal), or 2 unilocular, disjunct, basal.
  • Endocarp with surface smooth, bullate, rugose, or tuberculate, slightly striate or strongly costate.

Key differences from similar families

This family may be confused with Erythroxylaceae, Linaceae and Ixonanthaceae, but may be distinguished using the following key:

1. Shrubs or trees; flowers with calyx always gamosepalous and corolla with free petals; fruits drupe (or drupoid) … 2
1. Herbs, shrubs, trees or lianes; flowers with calyx gamosepalous or not, corolla gamopetalous or petals free; fruits capsule or drupoid … 3

2. Leaves alternate distichous, margins entire or not; stipules inconspicuous, persistent or deciduous; sepals ciliate at margins; stamens 10-200 connate at base; nectariferous intrastaminal free disk … Humiriaceae
2. Leaves alternate spiral; margins entire; stipules persistent, often aggregated; sepals not ciliate at margins; stamens 10, free or sometimes connate at base; disk absent … Erythroxylaceae

3. Herbal or woody plants; corolla gamopetalous or petal free;  stamens 5-10, connate at base; nectariferous disk present or absent; fruits capsules or drupoid … Linaceae
3. Woody plants (shrubs or trees); corolla with free petals; stamens 5-20, free; nectariferous intrastaminal disk present; fruits capsules … Ixonanthaceae

Number of genera

  • 8 genera: Duckesia, Endopleura, Humiria, Humiriastrum, Hylocarpa, Sacoglottis, Schistostemon, Vantanea.

Useful tips for generic identification

Key to genera of Neotropical Humiriaceae

1. Stamens 50-200, rarely 30-40, exceptionally 21-26; anthers with 2, bilocular thecae; style usually 2-12 mm high, exceptionally 0.6-0.7 or 1-1.5 or 30 mm high … Vantanea
1. Stamens 10-30; anthers with free, unilocular thecae; style 0.3-4 mm high … 2

2. Anther thecae 4, unilocular … 3
2. Anther thecae 2, unilocular … 4

3. Endocarp spongy-lignose, evenly costate with long, lingulate valves, resinous-lacunose; petals thick-membranaceus, linear-oblong, subacute, glabrous; stamens 20-25; ovary ovoid; style columnar, 1.5 mm high ... Duckesia (D. verrucosa (Ducke) Cuatrec.)
3. Endocarp prominently, sharply costate and furrowed with shorter, inconspicuous valves at bottom of furrows, compact-woody, not resinous-lacunose; petals rather thick, oblong, subacute or subobtuse, glabrous inside, hirtellous-pubescent outside; stamens 20-30; ovary subglobose; style stout, 0.9-1 mm high … Endopleura (E. uchi (Huber) Cuatrec.)

4. Stamens 30, anther connectives thick, very obtuseHylocarpa (H. heterocarpa (Ducke) Cuatrec.
4. Stamens 10-20, anther connectives attenuate, acute (rarely obtuse) … 5

5. Anther thecae pilose; carpels opposite petals, 2-ovulate ... Humiria
5. Anther thecae glabrous; carpels opposite sepals, 1-ovulate … 6

6. Stamens 10 … Sacoglottis
6. Stamens 20 … 7

7. Episepalous stamens 5, longer, trifurcate at apex, triantheriferous; epipetalous stamens 5, medium-sized, entire, monoantheriferous; 10 shorter alternate stamens monoantheriferous; style 0.3-1-(1.2) mm high; endocarp shallowly or inconspicuously furrowed, not foraminate at apex, resinous-lacunose, valves broad, adjacent, alternating ribs inconspicuous … Schistostemon
7. Stamens monoantheriferous, 10 episepalous and 10 epipetalous longer than alternating ones; style 0.5-0.7 mm high; endocarp 5-foraminate at apex, with 5 alternating, oblong and short opercular valves … Humiriastrum

Notable genera and distinguishing features

Status

  • Native.

General notes

  • Plants often with useful wood; some species present medicinal (bark and/or leaves) and edible (fruits) value. The balsamic sap and the oil of the seeds are of commercial value.

Important literature

Cuatrecasas, J. 1961. A taxonomic revision of the Humiriaceae. Contributions from the United States National Herbarium. 35 (2): 25-214.

Cuatrecasas, J. 1990. Miscellaneous notes on Neotropical Flora XVIII. New species in the Humiriaceae. Phytologia 68 (4): 260-266.

How to cite

Giordano, L.C.S. (2009). Neotropical Humiriaceae. In: Milliken, W., Klitgård, B. & Baracat, A. (2009 onwards), Neotropikey - Interactive key and information resources for flowering plants of the Neotropics. http://www.kew.org/science/tropamerica/neotropikey/families/Humiriaceae.htm.