Family Aquifoliaceae

Aquifoliaceae Bartl.

Alternatively Ilicaceae Brongn.

Excluding Phellinaceae, Sphenostemonaceae

Habit and leaf form. Small trees, or shrubs; not resinous; 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 evergreen; 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 (in one Ilex species); manifested as pockets.

Leaf anatomy. Mucilaginous epidermis present, or absent. Stomata mainly confined to one surface (abaxial); anomocytic.

Minor leaf veins without phloem transfer cells (Ilex).

Stem anatomy. Cork cambium present; initially superficial. Nodes unilacunar, or tri-lacunar. Internal phloem absent. Secondary thickening developing from a conventional cambial ring. ‘Included’ phloem absent. Xylem with fibre tracheids; with vessels. Vessel end-walls oblique; scalariform. Vessels without vestured pits. Wood parenchyma apotracheal (diffuse).

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

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 (1998) Eudicot; core Eudicot; Asterid; Euasterid II. APG 3 (2009) Order: Aquifoliales.

Species about 600. Genera 2; Ilex, Nemopanthus.

Our assignment of Aquifoliaceae to the Tenuinucelli (Young and Watson, 1970) is now well supported 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.

Illustrations.
• Technical details (Ilex aquifolium).
• Technical details (Ilex microphylla: Lindley).
• Ilex aquifolium (from B. Ent.).
• Ilex aquifolium: Eng. Bot. 316, 1864.

Quotations
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)

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