The families of flowering plants
Habit and leaf form. Small, Artocarpus-like trees, or shrubs. To 15–17 m high. Pachycaul, or leptocaul (more or less, with age). Leaves evergreen to deciduous (with intermittent leaf fall); alternate; spiral; flat; herbaceous, or leathery (?); petiolate; sheathing. Leaf sheaths not tubular; with free margins. Leaves simple. Lamina dissected; pinnatifid; pinnately veined; cross-venulate. Leaves exstipulate (though the petiole margins are spread). Lamina margins coarsely dentate, or entire; flat.
General anatomy. Plants with crystal sand (in epidermal and subepidermal leaf tissues, and in the stem).
Leaf anatomy. The leaf lamina dorsiventral. Stomata present; on both surfaces; anisocytic. Hairs present; eglandular and glandular; unicellular and multicellular. Unicellular hairs simple. Multicellular hairs uniseriate; simple. Complex hairs absent. Adaxial hypodermis absent. Lamina without secretory cavities. Main veins embedded.
Axial (stem, wood) anatomy. Pith heterogeneous (with sclereids). Secretory cavities absent. Cork cambium present; initially superficial. Nodes multilacunar. Cortical bundles present (reflecting the multilacunar nodes). Secondary thickening developing from a conventional cambial ring.
The wood diffuse porous. The vessel end-walls oblique; scalariform (with numerous bars). The axial xylem without fibre tracheids; with libriform fibres; frequently including septate fibres. The parenchyma paratracheal.
Reproductive type, pollination. Fertile flowers functionally male, or functionally female. Plants dioecious. Female flowers with staminodes (five). Gynoecium of male flowers absent.
Inflorescence, floral, fruit and seed morphology. Flowers aggregated in inflorescences; in panicles. The ultimate inflorescence units cymose. Inflorescences terminal; (both male and female) paniculate, the male plants with panicles of cymules of tiny flowers. Flowers bracteolate; regular; (male and female) 5 merous. Floral receptacle with neither androphore nor gynophore. Free hypanthium present, or absent (?).
Perianth with distinct calyx and corolla; 10; 2 whorled; isomerous. Calyx 5; 1 whorled; polysepalous, or gamosepalous (?); lobulate, or blunt-lobed; regular; persistent (?); non-accrescent; open in bud (?). Corolla 5; 1 whorled; polypetalous; slightly imbricate; regular.
Androecium 5. Androecial members free of the perianth; all equal (?); free of one another; 1 whorled. Androecium of male flowers, exclusively of fertile stamens. Stamens 5; isomerous with the perianth; oppositisepalous (?); filantherous. Anthers dorsifixed; dehiscing via longitudinal slits (?). Pollen grains aperturate; 3 aperturate; colporate.
Gynoecium 3(–4) carpelled (but pseudomonomerous, with 2(3) locules aborting). Carpels reduced in number relative to the perianth. The pistil 1 celled. Gynoecium syncarpous (with 2(3) locules aborting); synovarious (with 3(4) stylopodia and diverging styles); inferior. Ovary 1 locular (with the others aborting almost without trace). Epigynous disk present (of stylopodia). Gynoecium stylate. Styles 3(–4); free. Stigmas 3(–4). Placentation apical. Ovules differentiated; in the single cavity 1; funicled; pendulous; apotropous; with dorsal raphe; arillate; anatropous; unitegmic; tenuinucellate (the nucellus disintegrating by the time the sac is mature, save for a pedestal below it). Endothelium not differentiated (?). Embryo-sac development Polygonum-type (from a linear tetrad).
Fruit fleshy; indehiscent; a drupe (ovoid, the fleshy mesocarp about 5 mm thick). The drupes with one stone. Fruit 1 seeded. Seeds endospermic. Endosperm ruminate. Cotyledons 2. Embryo small, at the micropylar end.
Physiology, phytochemistry. C3. Anatomy non-C4 type. Anthraquinones not detected. Verbascosides detected (caffeic acid and unidentified derivatives Bate-Smith in Philipson et al. 1980). Iridoids detected; Route I type (cf. Griselinia in structure). Proanthocyanidins absent. Flavonols more or less absent (or traces of kaempferol). Ellagic acid absent (only caffeic acid and its derivatives found).
Geography, cytology. Paleotropical. Tropical. Thailand, Malaysia, Singapore, Sumatra, Anambas, Borneo.
Taxonomy. Subclass Dicotyledonae; Tenuinucelli. Dahlgrens Superorder Araliiflorae (re-assigned); Araliales. Cronquists Subclass Rosidae; Cornales. APG 3 core angiosperms; core eudicot; Superorder Asteranae; campanulid; Order Apiales (as a synonym of Torricelliaceae).
Species 1. Genera 1; only genus, Aralidium.
General remarks. See Philipson, Stone, Butterfield, Tseng, Jensen, Nielsen, Bate-Smith and Fairbrothers (1980). A genus on the Crassinucelli-Tenuinucelli borderline. The wood conforms with Araliaceae, but absence of secretory cavities, ovule orientation, iridoids, etc., seem cornaceous, and the pollen details are said to differ from both. rbcL sequence comparisons, however, seem to have settled the question in favour of Araliiflorae (cf. Backlund and Bremer, 1997). The data compiled here have the palaeotropical Arilidium differing conspicuously from the holarctic Toricellia (q.v.) in numerous characters representing leaf morphology and anatomy, vascular anatomy of the stem, wood anatomy, floral morphology (imbricate corolla, dorsifixed anthers, unilocular ovary, etc.), as well as in the ruminate endosperm.
Illustrations. • Aralidium pinnatifidum: Hook. Ic. Pl. 16 (1866–7).
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Cite this publication as: ‘Watson, L., and Dallwitz, M.J. 1992 onwards. The families of flowering plants: descriptions, illustrations, identification, and information retrieval. Version: 13th April 2016. delta-intkey.com’.