Lauraceae Juss.

Scientific Description

Common name. Laurel Family.

Habit and leaf form. Trees and shrubs (mainly), or lianas, or herbaceous climbers (Cassytha being represented by large, robust to small, soft parasitic twiners); usually evergreen; bearing essential oils, or without essential oils. ‘Normal’ plants (mostly), or switch-plants (Cassytha); Cassytha with the principal photosynthesizing function transferred to stems. Leaves well developed (usually), or much reduced (Cassytha). Autotrophic (usually), or partially parasitic (the dodderlike Cassytha). When parasitic, on aerial parts of the host (with haustoria). When herbaceous, perennial. Self supporting (usually), or climbing (Cassytha); the climbers stem twiners. Leptocaul. Mesophytic. Leaves alternate (usually), or opposite (rarely), or whorled (rarely); usually spiral; leathery (usually), or membranous (in Cassytha); petiolate; non-sheathing; gland-dotted; aromatic; simple. Leaf blades entire (usually), or dissected (lobed in e.g. Sassafras); when lobed, pinnatifid; pinnately veined; cross-venulate. Leaves without stipules; without a persistent basal meristem. Domatia recorded (14 genera); represented by pits (mostly), or pockets, or hair tufts. Stem anatomy. Nodes unilacunar (with two traces). Secondary thickening developing from a conventional cambial ring.

Reproductive type, pollination. Fertile flowers hermaphrodite, or functionally male and functionally female, or functionally male, or functionally female, or hermaphrodite, functionally male, and functionally female. Unisexual flowers present, or absent. Plants hermaphrodite, or monoecious, or dioecious, or polygamomonoecious.

Inflorescence and flower features. Flowers solitary (rarely), or aggregated in ‘inflorescences’. The terminal inflorescence unit racemose, or cymose. Inflorescences axillary; often umbelliform; with involucral bracts (often), or without involucral bracts. 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 sepaline (usually, relatively undifferentiated), or with distinct calyx and corolla (clearly, in Cassytha); 6 (usually), or 4; (1–)2(–3) -whorled; when more than one, isomerous; free to joined (there being a well developed hypanthium); green, or cream, or yellow; fleshy, or non-fleshy; persistent, or deciduous; accrescent, or non-accrescent. Calyx 3 (Cassytha), or (4–)6. Corolla in Cassytha, 3; 1 -whorled; regular; fleshy. Fertile stamens present, or absent (female flowers). 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). Stamens (3–)9(–26); diplostemonous to polystemonous (usually), or reduced in number relative to the adjacent perianth to isomerous with the perianth; laminar to petaloid (e.g. Cassytha), 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. Fertile gynoecium present, or absent (male flowers). Gynoecium 1 carpelled (ostensibly), or 3 carpelled (theoretically); 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; non-arillate; anatropous.

Fruit and seed features. Fruit fleshy (usually), or non-fleshy (very rarely). The fruiting carpel indehiscent; drupaceous, or baccate (usually), or nucular ((?) —rarely). Fruit enclosed in the fleshy receptacle, or enclosed in the fleshy hypanthium, or without fleshy investment; 1 seeded. Seeds non-endospermic. Embryo well differentiated (even in the parasitic Cassytha); achlorophyllous (5/6); straight. Seedling. Germination phanerocotylar, or cryptocotylar.

Physiology, biochemistry. Aluminium accumulation demonstrated.

Geography, cytology, number of species. World distribution: pantropical and subtropical, extending into the temperate regions. X = 12. 2000–2500 species.

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