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The families of flowering plants

L. Watson and M.J. Dallwitz

Tofieldiaceae Takht.

~ Former Liliaceae, Melanthiaceae.

Habit and leaf form. Herbs. Leaves well developed. Plants autotrophic, or parasitic (rarely); if parasitic, mycoheterotrophic; green and photosynthesizing. Annual (rarely), or perennial; with a basal aggregation of leaves, or without conspicuous aggregations of leaves; rhizomatous (mainly), or tuberous, or cormous (rarely). Leaves alternate; spiral (usually), or distichous; flat; ‘herbaceous’; sessile (usually), or petiolate (occasionally, almost); sheathing. Leaf sheaths not tubular. Leaves without marked odour; borne edgewise to the stem; simple. Lamina entire; linear to lanceolate (usually), or ovate (rarely); parallel-veined. Leaves ligulate (Pleea), or eligulate.

Leaf anatomy. The leaf lamina bifacial. The mesophyll commonly containing crystals. The crystals raphides, or solitary-prismatic. Foliar vessels absent.

Axial (stem, wood) anatomy. Secondary thickening absent. The axial xylem without vessels.

Root anatomy. Root xylem with vessels; vessel end-walls scalariform.

Reproductive type, pollination. Plants hermaphrodite (nearly always), or dioecious, or polygamomonoecious. Floral nectaries present. Nectar secretion from the gynoecium (Tofieldia with septal nectaries).

Inflorescence, floral, fruit and seed morphology. Flowers aggregated in ‘inflorescences’; in racemes, or in spikes, or in panicles. Inflorescences scapiflorous, or scapiflorous to not scapiflorous; spikes, racemes or corymbose cymes. Flowers bracteate, or ebracteate; regular (nearly always); 3 merous; cyclic; pentacyclic. Perigone tube present to absent. Hypogynous disk absent.

Perianth of ‘tepals’; 6; free to joined (the perianth segments spreading, distinct or shortly basally connate); 2 whorled (3+3); isomerous; sepaloid, or petaloid; without spots, or spotted (occasionally); similar in the two whorls; green to white, or cream, or purple, or brown (usually inconspicuous, usually lacking patterns and spurs).

Androecium 6, or 9 (Pleea), or 12 (Pleea). Androecial members more or less 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 12 (Pleea); diplostemonous (usually), or triplostemonous to polystemonous (Pleea); normally alterniperianthial; filantherous (or the filaments sometimes somewhat flattened). Anthers dorsifixed (hypopeltate), or basifixed; versatile; dehiscing via longitudinal slits; introrse. Endothecium developing fibrous thickenings. The endothecial 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 carpelled. Carpels isomerous with the perianth. The pistil 3 celled. Gynoecium syncarpous; semicarpous (the carpels free above, and in Isidrogalvia free almost to their bases), or synovarious (with separate styles), or eu-syncarpous (some Tofieldia with one style and a capitate stigma); superior, or partly inferior. Carpel 2–100 ovuled (to ‘many’). Placentation marginal. Ovary when syncarpous, 3 locular; sessile. Gynoecium stylate. Styles 1, or 3; when three, free; apical. Stigmas 1, or 3. Placentation axile. Ovules 2–100 per locule (to ‘many’); funicled; non-arillate; at least, usually anatropous; 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. Endosperm formation helobial (by contrast with Liliales).

Fruit non-fleshy; an aggregate, or not an aggregate. The fruiting carpel when semicarpous, dehiscent. Fruit dehiscent; a capsule. Capsules septicidal. Seeds endospermic. Endosperm oily. Seeds usually winged (or with terminal appendages), or wingless. Embryo well differentiated (but often small). Embryo ovoid or globose. Testa without phytomelan (by conrast with most capsular Asparagales, and also lacking phlobaphene).

Seedling. Hypocotyl internode present, or absent. Seedling collar not conspicuous. Cotyledon hyperphyll elongated; assimilatory; more or less circular in t.s., or dorsiventrally flattened (variously unifacial or bifacial). Coleoptile absent. Seedling cataphylls absent. First leaf ensiform (e.g. Tolfieldia). Primary root ephemeral.

Physiology, phytochemistry. Inulin recorded (Gibbs 1974). Not cyanogenic. Alkaloids absent. Saponins/sapogenins often present. Proanthocyanidins present, or absent; when present, cyanidin. Flavonols present, or absent; when present, kaempferol and quercetin. Ellagic acid absent.

Geography, cytology. Holarctic and Neotropical. Frigid zone and temperate. N. temperate, S.E. U.S.A., Venezuela, Guiana, Andes, arctic, sub-arctic. Chromosomes with normal centromeres.

Taxonomy. Subclass Monocotyledonae. Dahlgren et al. Superorder Liliiflorae; Melanthiales. APG III core angiosperms; Superorder Lilianae; non-commelinid Monocot. APG IV Order Alismatales.

Species about 30. Genera 4; Isidrogalvia (inc. Harperocallis), Pleea, Tofieldia, Triantha.

General remarks. An excellent treatment of Melanthiaceae sensu lato by Zomlefer (1997) is not accounted for here.

Illustrations. • Pleea tenuifolia: Curtis Bot. Mag. 1956 (1815). • Le Maout and Decaisne: Veratrum, Tofieldia, Amianthium (= Zigadenus). • Tofieldia calyculata: Hutchinson (1964). • Tofieldia palustris: Eng. Bot. 1543 (1869). • Isidrogalvia sessiliflora: Hook. Ic. Pl. 7–8 (1844).

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: 5th March 2018.’.