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The families of flowering plants

L. Watson and M.J. Dallwitz

Aquifoliaceae Bartl.

Alternatively Ilicaceae Brongn.

Excluding Phellinaceae, Sphenostemonaceae.

Habit and leaf form. Small trees, or shrubs; not resinous. Plants green and photosynthesizing. Leptocaul. Commonly heterophyllous (at least in Ilex aquifolium, which commonly exhibits unarmed leaves on mature shoots, cf. irreversible maturation in Hedera), or not heterophyllous. Leaves usually persistent; alternate, or opposite (rarely), or whorled (rarely in ‘pseudowhorls’); usually spiral; leathery; petiolate; non-sheathing; simple. Lamina dissected, or entire; when dissected, pinnatifid, or spinose; pinnately veined; cross-venulate. Leaves stipulate (stipules small), or exstipulate (?). Stipules caducous (often), or persistent. Lamina margins dentate (often prickly), or entire. Domatia occurring in the family (recorded in one Ilex species); manifested as pockets.

Leaf anatomy. Mucilaginous epidermis present, or absent. Stomata mainly confined to one surface (abaxial); anomocytic. Hairs present (rarely), or absent; when found, eglandular; unicellular (usually), or multicellular (in some Ilex spp.). Unicellular hairs simple (with the lumina more or less obliterated). Multicellular hairs where present, uniseriate; simple (long and thin-walled). Complex hairs absent. The mesophyll containing crystals. The crystals exclusively druses. Minor leaf veins without phloem transfer cells (Ilex).

Axial (stem, wood) anatomy. Secretory cavities absent. Cork cambium present; initially superficial. Nodes unilacunar, or tri-lacunar. Primary vascular tissues in a cylinder, without separate bundles, or comprising a ring of bundles (commonly traversed by broad rays); collateral. Internal phloem absent. Cortical bundles absent. Medullary bundles absent. Secondary thickening developing from a conventional cambial ring. Primary medullary rays commonly wide.

The wood ring porous to diffuse porous. The vessels mostly small (sometimes extremely so), or small to medium; solitary, or radially paired, or in radial multiples, or clustered, or in tangential arcs. The vessel end-walls oblique; scalariform. The vessels without vestured pits; with spiral thickening. The axial xylem with tracheids; without vasicentric tracheids; with fibre tracheids; without septate fibres. The fibres with spiral thickening, or without spiral thickening. The parenchyma apotracheal (diffuse). ‘Included’ phloem absent. The wood not storied.

Reproductive type, pollination. Unisexual flowers present. Plants dioecious, or polygamomonoecious. Female flowers with staminodes (four, these sometimes petaloid).

Inflorescence, floral, fruit and seed morphology. Flowers aggregated in ‘inflorescences’, or solitary (rarely); when solitary, axillary; when aggregated, in cymes, in fascicles, and in panicles. The ultimate inflorescence units cymose. Inflorescences cymes or fascicles, rarely racemes. Flowers regular; 4(–8) merous. Free hypanthium absent. Hypogynous disk absent.

Perianth with distinct calyx and corolla, or sepaline, or petaline, or vestigial; 0, or 4–5, or 8; 1 whorled, or 2 whorled; isomerous, or anisomerous. Calyx 4–5, or 8; 1 whorled; gamosepalous; imbricate. Corolla if present, 4–5, or 8; 1 whorled; gamopetalous (at the base), or polypetalous. Corolla lobes markedly longer than the tube. Corolla imbricate.

Androecium 4–5, or 8(–12). Androecial members free of the perianth to adnate (usually adnate to the corolla base); free of one another; 1–3 whorled. Androecium exclusively of fertile stamens. Stamens 4, or 8(–12); isomerous with the perianth to triplostemonous; oppositisepalous. Anthers dehiscing via longitudinal slits; introrse; tetrasporangiate. Tapetum probably glandular. Pollen grains aperturate, or nonaperturate; when aperturate, 3(–4) aperturate; colporate (colporoidate); 2-celled.

Gynoecium (2–)4–6(–24) carpelled. Carpels isomerous with the perianth. The pistil (2–)4–6(–24) celled. Gynoecium syncarpous; eu-syncarpous; superior. Ovary (2–)4–6(–24) locular. Gynoecium non-stylate to stylate. Styles if detectable, 1. Stigmas wet type; non-papillate; Group IV type. Placentation apical. Ovules 1(–2) per locule; funicled; pendulous; apotropous (Engler); with dorsal raphe; non-arillate (? — if a funicular protuberance sometimes seen represents the second, usually abortive ovule); anatropous (usually), or campylotropous; unitegmic; crassinucellate (usually), or tenuinucellate (reported in two Ilex spp.). Endothelium differentiated. Embryo-sac development Polygonum-type. Polar nuclei fusing prior to fertilization. Antipodal cells formed; 3; not proliferating; persistent. Synergids pear-shaped. Endosperm formation cellular. Embryogeny caryophyllad.

Fruit fleshy; indehiscent; a drupe. The drupes with separable pyrenes (as many pyrenes as locules). Seeds richly endospermic. Endosperm oily (and proteinaceous). Cotyledons 2. Embryo achlorophyllous (2/2); straight.

Seedling. Germination phanerocotylar.

Physiology, phytochemistry. C3. C3 physiology recorded directly in Ilex. Sugars transported as oligosaccharides + sucrose, or as sugar alcohols + oligosaccharides + sucrose. Cyanogenic, or not cyanogenic. Alkaloids present, or absent (mostly). Arbutin absent. Iridoids not detected. Saponins/sapogenins present, or absent. Proanthocyanidins absent. Flavonols present; kaempferol and quercetin. Ellagic acid absent (Ilex). Ursolic acid present. Aluminium accumulation not found.

Geography, cytology. Temperate, sub-tropical, and tropical. Widespread. 2n = 17–20 (Ilex), 40 (Nemopanthus); X = 9, 10.

Taxonomy. Subclass Dicotyledonae; Tenuinucelli. Dahlgren’s Superorder Corniflorae; Cornales. Cronquist’s Subclass Rosidae; Celastrales. APG III core angiosperms; core eudicot; Superorder Asteranae; campanulid. APG IV Order Aquifoliales.

Species about 600. Genera 2; Ilex, Nemopanthus.

General remarks. Readily separable from Phellinaceae (q.v.) only via calyx and corolla characters, but seemingly differing in wood anatomy as well. Our assignment of Aquifoliaceae to the Tenuinucelli (Young and Watson, 1970) was well supported - without acknowledgement - by rbcL sequencing studies (e.g. Chase et al. 1993).

Economic uses, etc. Ilex species supply hard, white, fine-grained wood, used for inlay work and sometimes stained black as ebony substitute; Maté or Paraguay tea from dried leaves of I. paraguensis; many species and hybrids used as ornamentals.


Then heigh-ho! The holly!
This life is most jolly!
(‘As You Like It’, ii., 7)

Below, a circling fence, its leaves are seen
Wrinkled and keen;
No grazing cattle through their prickly round
Can reach to wound;
But as they grow where nothing is to fear,
Smooth and unarm’d the pointless leaves appear
(Robert Southey, ‘The Holly-tree’ - re. heterophylly)

Tho’ winter blasts blow never so hye,
Green groweth the holly
(King Henry VIII, 1491–1547)

Illustrations. • Le Maout and Decaisne: Ilex aquifolium. • Ilex microphylla: Lindley. • Ilex affinis: Hook. Ic. Pl. 5–6 (1842–3). • Ilex aquifolium (from B. Ent., 1825). • Ilex aquifolium: Eng. Bot. 316, 1864. • Ilex microphylla: Hook. Ic. Pl. 2 (1837). • Ilex denticulata: R. Wight 2 (1850).

We advise against extracting comparative information from the descriptions. This is much more easily achieved using the DELTA data files or the interactive key, which allows access to the character list, illustrations, full and partial descriptions, diagnostic descriptions, differences and similarities between taxa, lists of taxa exhibiting or lacking specified attributes, distributions of character states within any set of taxa, geographical distribution, genera included in each family, and classifications (Dahlgren; Dahlgren, Clifford, and Yeo; Cronquist; APG). See also Guidelines for using data taken from Web publications.

Cite this publication as: ‘Watson, L., and Dallwitz, M.J. 1992 onwards. The families of flowering plants: descriptions, illustrations, identification, and information retrieval. Version: 5th March 2018.’.