Alliaceae J.G. Agardh

~ Liliaceae

Including Themid(ac)eae Salisb.

Habit and leaf form. Herbs; laticiferous (mucilaginous, e.g. in Allium), or non-laticiferous and without coloured juice; bearing essential oils, or without essential oils. Perennial; with a basal aggregation of leaves (but sometimes the leaves long-sheathed so as to appear cauline); bulbaceous, or cormous, or rhizomatous (rarely - e.g. Agapanthus). Mesophytic, or xerophytic. Leaves not evergreen; alternate; spiral, or distichous; flat, or rolled, or terete (or angular); sessile (usually), or petiolate (rarely, e.g. Allium ursinum); sheathing. Leaf sheaths with free margins. Leaves aromatic (often onion-scented, with allylic sulphides), or without marked odour; simple; epulvinate. Lamina entire; linear, or lanceolate, or ovate (rarely); parallel-veined, or palmately veined, or pinnately veined (then pinnate-parallel); without cross-venules.

General anatomy. Plants with laticifers (articulated), or without laticifers. The laticifers of Allium, in leaves (in the inner chlorenchyma).

Leaf anatomy. Stomata present; anomocytic.

The mesophyll containing calcium oxalate crystals, or without calcium oxalate crystals (? - `raphides sometimes present, sometimes absent'). Minor leaf veins without phloem transfer cells (Allium, Triteleia).

Stem anatomy. Secondary thickening absent. Xylem without vessels. Sieve-tube plastids P-type; type II.

Root anatomy. Root xylem with vessels. Vessel end-walls scalariform and simple (mainly simple, by contrast with Amaryllidaceae).

Reproductive type, pollination. Hermaphrodite. Floral nectaries present. Nectar secretion from the gynoecium (from septal nectaries). Entomophilous.

Inflorescence, floral, fruit and seed morphology. Flowers aggregated in `inflorescences' (usually), or solitary (Ipheion); in umbels. The terminal inflorescence unit cymose. Inflorescences scapiflorous; umbellate, usually representing one or more contracted, helicoid cymes; with involucral bracts (the umbel surrounded by (1-)2(to several) bracts); spatheate (with reference to the one to several spathal involucral bracts). Flowers fragrant, or odourless; regular to somewhat irregular. The floral asymmetry e.g. in some Allium species, involving the androecium. Flowers 3 merous; cyclic; pentacyclic. Perigone tube present, or absent.

Perianth of `tepals'; 6; free to joined; 2 whorled (3+3); isomerous; petaloid; similar in the two whorls; white, or violet, or blue, or purple, or yellow, or green and white, or brown and white, or white and red.

Androecium 6. Androecial members adnate (at the base of the tepals, or to the tube); all equal (mostly), or markedly unequal (Ipheion); free of one another (mostly), or coherent (the filaments sometimes basally cohering in Allium); 2 - whorled (3+3). Androecium exclusively of fertile stamens (usually), or including staminodes. Staminodes when present, 3, or 4. Stamens 6 (usually), or 2-3 (e.g. the Gilliesia group, Leucocoryne); isomerous with the perianth (usually), or reduced in number relative to the adjacent perianth; al\ter\ni\peri\anthial, or op\po\siti\peri\anthial (sometimes even when six-stamened - e.g. see Dahlgren et al. 1985, drawings of Tritagma, p. 197); filantherous (the filaments flat). Filaments appendiculate, or not appendiculate. Anthers dorsifixed; dehiscing via longitudinal slits; introrse. Endothecium developing fibrous thickenings. The thickenings spiral. Microsporogenesis successive. Tapetum glandular. Pollen grains aperturate; 1 - aperturate; sulcate; 2-celled.

Gynoecium 3. Carpels isomerous with the perianth. Gynoecium syncarpous; synstylovarious, or eu-syncarpous; superior. Ovary 3 locular. Gynoecium stylate. Styles 1; apical. Stigmas wet type, or dry type; papillate. Placentation axile. Ovules 1-50 per locule (to `many'); campylotropous (usually), or anatropous; tenuinucellate, or crassinucellate (e.g. Agapanthus). Embryo-sac development Polygonum-type, or Allium-type. Antipodal cells formed; 3; not proliferating; ephemeral. Hypostase present. Endosperm formation nuclear, or helobial.

Fruit non-fleshy; dehiscent; a capsule. Seeds endospermic. Endosperm oily. Seeds without starch. Cotyledons 1. Embryo achlorophyllous (2/5); straight to curved. Testa encrusted with phytomelan.

Physiology, biochemistry. Cyanogenic (?), or not cyanogenic. Alkaloids absent. Proanthocyanidins absent (12 species). Flavonols present (mostly), or absent (e.g. Agapanthus); kaempferol, or kaempferol and quercetin. Ellagic acid absent. Saponins/sapogenins present. Inulin recorded (Allium, Gibbs 1974). C3. C3 recorded in Allium. Anatomy non-C4 type (Allium).

Geography, cytology. Holarctic, Paleotropical, and Neotropical. Temperate, sub-tropical, and tropical. Cosmopolitan, but few in Australasia.

Taxonomy. Subclass Monocotyledonae. Superorder Liliiflorae; Asparagales. Species 600. Genera 30 (according to Dahlgren et al. 1985, who list only the following); Allium, Androstephium, Agapanthus, Brodiaea, Dichellostemma, Gilliesia, Ipheion, Leucocoryne, Nothoscordum, Milla, Muilla, Scadoxus, Solaria, Tristagma, Triteleia, Tulbaghia.

Economic uses, etc. Allium spp. supply onions and garlic.

Illustrations. allia196.gif allia844.gif