~ Liliaceae
Including Petrosaviaceae Hutch.
Habit and leaf form. Herbs. Leaves well developed, or much reduced (Petrosavieae). Autotrophic, or saprophytic (Petrosavieae). Annual (rarely), or perennial; with a basal aggregation of leaves, or with neither basal nor terminal aggregations of leaves; rhizomatous (mainly), or tuberous, or cormous (rarely). Leaves alternate; spiral (usually), or distichous; flat; `herbaceous', or membranous (Petrosavieae); sessile (usually), or petiolate (occasionally, almost); sheathing. Leaf sheaths not tubular. Leaves edgewise to the stem, or with `normal' orientation; simple. Lamina linear to lanceolate (usually), or ovate (rarely); parallel-veined. Leaves ligulate (Pleea), or eligulate.
Leaf anatomy. Lamina dorsiventral, or isobilateral. The mesophyll containing mucilage cells (? - with raphides); commonly containing calcium oxalate crystals. The mesophyll crystals raphides. Vessels absent.
Stem anatomy. Secondary thickening absent. Xylem without vessels.
Root anatomy. Root xylem with vessels, or without vessels (in achlorophyllous forms). Vessel end-walls scalariform.
Reproductive type, pollination. Hermaphrodite (nearly always), or dioecious, or polygamomonoecious. Floral nectaries present. Nectar secretion from the perianth (from the tepal bases in Narthecieae), or from the gynoecium (Petrosavia, Tofieldia, Zigadenus etc. with septal nectaries).
Inflorescence, floral, fruit and seed morphology. Flowers aggregated in `inflorescences'; in racemes, or in spikes, or in panicles. Inflorescences scapiflorous, or not scapiflorous; simple or compound racemes or spikes, rarely panicles; espatheate. Flowers bracteate, or ebracteate; regular (nearly always), or very irregular (only in Chionographis); in Chionographis, zygomorphic; 3 merous; cyclic; usually pentacyclic. Perigone tube present (in hemi-epigynous forms), or absent. Hypogynous disk absent.
Perianth of `tepals'; 6; free to joined; 2 whorled (3+3); isomerous; sepaloid, or petaloid; without spots, or spotted (occasionally); similar in the two whorls; white, or yellow, or brown, or purple (bright yellow in Narthecium, but usually inconspicuous, usually lacking patterns and spurs).
Androecium 6, or 9 (Pleea), or 12 (Pleea). Androecial members free of the perianth; free of one another; 2 - whorled (usually 3+3, Pleea with 6+3 or 6+6). Androecium exclusively of fertile stamens. Stamens 6 (usually), or 9 (Pleea), or 12 (Pleea); diplostemonous (usually), or triplostemonous to polystemonous (Pleea); normally al\ter\ni\peri\anthial. Anthers dorsifixed (hypopeltate), or basifixed; dehiscing via longitudinal slits; extrorse (usually), or introrse (occasionally). Endothecium developing fibrous thickenings. The thickenings spiral. Microsporogenesis successive (usually), or simultaneous (Tofieldia). Anther wall initially with more than one middle layer; of the `monocot' type. Tapetum glandular. Pollen grains aperturate; 1 - aperturate (usually), or 2 - aperturate, or 4 - aperturate; sulcate (usually), or sulculate, or foraminate; 2-celled.
Gynoecium 3. Carpels isomerous with the perianth. Gynoecium apocarpous to syncarpous; semicarpous (the carpels often free above, and in Petrosavieae and Harperocallis free almost to their bases), or synovarious (usually, with separate styles), or synstylovarious (Aletris, with a tribrachiate style), or eu-syncarpous (sometimes, e.g. Tofieldia, with one style and a capitate stigma); superior, or partly inferior. Carpel when semicarpous, stylate; 2-100 ovuled (to `many'). Placentation marginal. Ovary when syncarpous, 3 locular; sessile. Gynoecium stylate. Styles 1, or 3; when three, free, or partially joined; apical. Stigmas 1, or 3; of Veratrum dry type. Placentation axile. Ovules 2-100 per locule (to `many'); funicled; non-arillate; anatropous (usually), or campylotropous (Petrosavia); bitegmic; crassinucellate. Outer integument not contributing to the micropyle. Endothelium differentiated. Embryo-sac development Polygonum-type. Polar nuclei fusing prior to fertilization. Antipodal cells formed; proliferating (Veratrum). Endosperm formation helobial (by contrast with Liliales).
Fruit non-fleshy. The fruiting carpel when semicarpous, dehiscent; a follicle (opening along the inner suture). Fruit when syncarpous, dehiscent; a capsule. Capsules septicidal, or loculicidal (or opening ventricidally from apex to base, when the carpels are distally free, e.g. Tofieldia, Veratrieae). Seeds endospermic. Endosperm oily. Seeds usually winged (or with terminal appendages). Embryo well differentiated (but often small). Embryo ovoid or globose. Testa without phytomelan (by conrast with most capsular Asparagales, and also lacking phlobaphene).
Physiology, biochemistry. Not cyanogenic. Alkaloids present (Veratreae), or absent. Proanthocyanidins present, or absent; when present, cyanidin. Flavonols present, or absent; when present, kaempferol and quercetin. Ellagic acid absent. Saponins/sapogenins often present. Inulin recorded (Gibbs 1974).
Geography, cytology. Holarctic (mainly), or Paleotropical, or Neotropical. Frigid zone, or temperate (mainly). Widespread N. temperate, E. Asia, Malaya, Borneo, the Americas, Arctic - not Africa, not Australia. X = 8, 11, 12, 13, 15, 17.
Taxonomy. Subclass Monocotyledonae. Superorder Liliiflorae; Melanthiales. Species about 140. Genera 21; Aletris, Amianthium, Chamaelirium, Chionographis, Harperocallis, Helonias, Heloniopsis, Lophiola, Narthecium, Nietneria, Melanthium, Metanarthecium, Petrosavia, Pleea, Protolirion, Schoenocaulon, Stenanthium, Tofieldia, Veratrum, Zigadenus, Xerophyllum.
Illustrations. melan851.gif melan862.gif
