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The families of flowering plants

L. Watson and M.J. Dallwitz

Lauraceae Juss.

Including Perseaceae Horan.; excluding Cassythaceae.

Habit and leaf form. Trees and shrubs (frequently aromatic); commonly bearing essential oils, or without essential oils. ‘Normal’ plants. Leaves well developed (usually). Self supporting. Leptocaul. Mesophytic. Leaves nearly always persistent; alternate (usually), or opposite (rarely), or whorled (rarely); usually spiral; leathery; petiolate; non-sheathing; gland-dotted; aromatic; simple. Lamina entire (usually), or dissected (lobed in e.g. Sassafras); when lobed, pinnatifid; pinnately veined; cross-venulate. Leaves exstipulate; leaf development not ‘graminaceous’. Domatia occurring in the family (seen in 14 genera); manifested as pits (mostly), or pockets, or hair tufts.

Leaf anatomy. The leaf lamina dorsiventral (usally), or bifacial (occasionally with the abaxial palisade developed more strongly than the adaxial). Stomata mainly confined to one surface (abaxial, often sunken); paracytic. Hairs present; mostly unicellular (and mostly thick walled). Complex hairs seemingly absent. Adaxial hypodermis present (not uncommonly), or absent. Lamina without secretory cavities. The mesophyll usually with spherical etherial oil cells; not containing mucilage cells (less common than oil cells), or not containing mucilage cells; containing crystals. The crystals mostly solitary-prismatic (usually in the form of small needles or spindles). Minor leaf veins without phloem transfer cells (Cinnamomum, Laurus, Persea).

Axial (stem, wood) anatomy. Cork cambium present (generally becoming ative late); initially superficial (usually), or initially deep-seated. Nodes unilacunar (with two or three traces). Primary vascular tissues in a cylinder, without separate bundles; collateral. Internal phloem absent. Cortical bundles absent. Medullary bundles absent. Secondary thickening developing from a conventional cambial ring. Primary medullary rays narrow (usually), or mixed wide and narrow.

The wood ring porous (rarely, e.g. sometimes in Sassafras), or diffuse porous. The vessels small (in a few species), or medium (mostly); solitary, radially paired, and in radial multiples, or in tangential arcs (mostly solitary and in numerous small radial multiples, but multiples of 4 or more cells and oblique rows also occur in some genera). The vessel end-walls scalariform, or simple, or scalariform and simple. The vessels without vestured pits; without spiral thickening. The axial xylem with tracheids, or without tracheids; with vasicentric tracheids (rarely), or without vasicentric tracheids; with fibre tracheids, or without fibre tracheids (usually); with libriform fibres (usually), or without libriform fibres; including septate fibres (commonly), or without septate fibres. The parenchyma paratracheal. The secondary phloem not stratified. ‘Included’ phloem absent. The wood partially storied (VPI), or not storied.

Reproductive type, pollination. Plants hermaphrodite, or monoecious, or dioecious, or polygamomonoecious.

Inflorescence, floral, fruit and seed morphology. Flowers solitary (rarely), or aggregated in ‘inflorescences’. The ultimate inflorescence units cymose, or racemose. Inflorescences axillary; often umbelliform; with involucral bracts (often), or without involucral bracts. The involucres accrescent, or non-accrescent. Flowers small; often fragrant; regular; usually 3 merous; cyclic. Free hypanthium present (well developed, like a calyx tube, at least after fertilization). Hypogynous disk present, or absent.

Perianth with distinct calyx and corolla, or sepaline, or of ‘tepals’ (the two similar, more or less sepaloid whorls variously interpreted as ‘tepals’ or ‘sepals’, hence the clumsy complexity of what follows); 6 (usually), or 4; free (but on a well developed hypanthium); (1–)2(–3) whorled; when more than one whorl, isomerous; sepaloid to petaloid; similar in the two whorls; green, or white, or cream, or yellow; fleshy, or non-fleshy; persistent, or deciduous; accrescent, or non-accrescent. Calyx if the P so interpreted, (4–)6; usually 2 whorled; polysepalous (on the hypanthium); regular; imbricate. Corolla if the inner P whorl so interpreted, 3; 1 whorled; polypetalous; imbricate; regular; green, or white, or yellow; fleshy. Petals sessile.

Androecium (3–)9(–26). Androecial members free of the perianth (on the hypanthium); all equal, or markedly unequal; free of one another; (1–)3 whorled, or 4 whorled. Androecium exclusively of fertile stamens, or including staminodes (the innermost members often staminodal, and sometimes there are paired, nectariferous ?staminodal appendages on the filaments). Staminodes internal to the fertile stamens (in 1–2 whorls). Stamens (3–)9(–26); diplostemonous to polystemonous (usually), or reduced in number relative to the adjacent perianth to isomerous with the perianth; somewhat laminar to petaloid (by expansion of the filament and connective), or filantherous. Filaments appendiculate (the appendages paired, nectariferous), or not appendiculate. Anthers basifixed; non-versatile; dehiscing by longitudinal valves (opening from base to apex), or dehiscing via pores (in Hexapora); introrse (usually), or introrse and extrorse (with the latter state confined to the third whorl); bilocular, or four locular; bisporangiate, or tetrasporangiate, or bisporangiate and tetrasporangiate. Endothecium developing fibrous thickenings (or the cell walls become much thickened). Anther epidermis persistent. Microsporogenesis successive. The initial microspore tetrads tetrahedral (usually, predominantly), or isobilateral, or T-shaped, or linear. Anther wall initially with more than one middle layer (two, plus an endothecium); of the ‘basic’ type. Tapetum amoeboid (mostly), or glandular (in several genera). Pollen grains nonaperturate; 2-celled (in 4 genera).

Gynoecium 1 carpelled (ostensibly), or 3 carpelled (theoretically). The pistil 1 celled. Gynoecium ostensibly monomerous; of one carpel (or at least, ostensibly so); superior (usually), or inferior (Hypodaphnis). Carpel stylate; apically stigmatic; 1 ovuled. Placentation apical. Stigmas dry type; papillate; Group II type. Ovules pendulous; apotropous; with dorsal raphe; non-arillate; anatropous; bitegmic; crassinucellate. Outer integument not contributing to the micropyle. Endothelium at least usually not differentiated (dubiously present in Beilschmiedia pendula). Embryo-sac development Polygonum-type. Polar nuclei fusing prior to fertilization. Antipodal cells formed, or not formed (then the three nuclei degenerating early); when formed, 3; proliferating (rarely), or not proliferating. Synergids commonly exhibiting filiform apparatus. Hypostase present (in a few genera only), or absent. Endosperm formation nuclear. Endosperm haustoria present, or absent; micropylar (where observed, in Cryprocarya). Embryogeny onagrad, or asterad, or piperad (or with no clear pattern).

Fruit fleshy (usually), or non-fleshy (very rarely). The fruiting carpel indehiscent; drupaceous, or baccate (usually). Fruit enclosed in the fleshy receptacle, or enclosed in the fleshy hypanthium, or without fleshy investment external to the original ovary; 1 seeded. Seeds non-endospermic. Embryo well differentiated. Cotyledons massive, occasionally ruminate. Embryo achlorophyllous (5/6); straight.

Seedling. Germination phanerocotylar, or cryptocotylar.

Physiology, phytochemistry. Sugars transported as sucrose (e.g. Miscanteca (= Licaria)), or as oligosaccharides + sucrose (e.g. Sassafras), or as sugar alcohols + oligosaccharides + sucrose (e.g. Cinnamomum). Inulin recorded. Not cyanogenic. Alkaloids present (commonly), or absent. Arbutin absent. Iridoids not detected. Saponins/sapogenins absent. Proanthocyanidins present (usually), or absent; when present, cyanidin. Flavonols present; kaempferol and quercetin. Ellagic acid absent (8 species, 7 genera). Aluminium accumulation demonstrated. Sieve-tube plastids P-type, or S-type; when P-type type I (b).

Geography, cytology. Temperate to tropical. Pantropical and subtropical, extending into the temperate regions. X = 12.

Taxonomy. Subclass Dicotyledonae; Crassinucelli. Dahlgren’s Superorder Magnoliiflorae; Laurales. Cronquist’s Subclass Magnoliidae; Laurales. APG III core angiosperms; Superorder Magnolianae. APG IV Order Laurales.

Species 2000–2500. Genera 54; Actinodaphne, Adenodaphne, Aiouea, Alseodaphne, Anaueria, Aniba, Apollonias, Aspidostemon, Beilschmiedia, Brassiodendron, Caryodaphnopsis, Chlorocardium, Cinnadenia, Cinnamomum, Clinostemon, Cryptocarya, Dehaasia, Dicypellium, Dodecadenia, Endiandra, Endlicheria, Eusideroxylon, Gamanthera, Hexapora, Hypodaphnis, Iteadaphne, Kubitzkia, Laurus, Licaria, Lindera, Litsea, Machilus, Mezilaurus, Nectandra, Neocinnamomum, Neolitsea, Nothaphoebe, Ocotea, Paraia, Persea, Phoebe, Phyllostemonodaphne, Pleurothyrium, Potameia, Potoxylon, Povedadaphne, Ravensara, Rhodostemonodaphne, Sassafras, Syndiclis, Triadodaphne, Umbellularia, Urbanodendron, Williamodendron.

Economic uses, etc. Some important economic plants, including fruit from Persea americana (Avocado pear), cinnamon and camphor from Cinnamomum spp., aromatic oils oils from Lindera (benzoin) and Sassafras, and fragrant woods used in cabinet-making.

Illustrations. • Le Maout and Decaisne: Laurus nobilis, Cinnamomum. • Litsea baueri: Lindley. • Alseodaphne perakensis, as Stemmatodaphne: Hook. Ic. Pl. 30 (1913). • Aniba perutilis: Hook. Ic. Pl. 25 (1896). • Hypodaphnis zenkeri: Hook. Ic. Pl. 30 (1911). • Machilus thunbergii: Hook. Ic. Pl. 26 (1897). • Ocotea usambarensis: Hook. Ic. Pl. 30 (1911). • Persea gratissima: Bot. Reg. 1258 (1829). • Mezilaurus ita-uba, as Misanteca anacardioides: Hook. Ic. Pl. 13 (1877–79). • Potameia paradoxa, as Syndiclis: Hook. Ic. Pl. 16 (1886). • Sassafras tzumu: Hook. Ic. Pl. 29 (1907).

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: 15th April 2018.’.