| # The Families of Angiosperms |

L. Watson and M.J. Dallwitz

### Butomaceae Rich.

Habit and leaf form. Herbs; laticiferous. Perennial; with a basal aggregation of leaves; rhizomatous (monopodial). Hydrophytic to helophytic. Leaves emergent. Leaves alternate; distichous (at least in origin); petiolate, or sessile; sheathing. Leaf sheaths not tubular; with free margins. Leaves simple. Lamina entire; linear (more or less triquetrous, twisted); parallel-veined. Axillary scales present. Lamina margins entire.

General anatomy. Plants without laticifers (but with laticiferous canals).

Leaf anatomy. Stomata present; paracytic. Guard-cells not ‘grass type’. Lamina with secretory cavities. Secretory cavities containing latex; schizogenous. The mesophyll containing crystals, or without crystals (? — no raphides). Foliar vessels absent.

Axial (stem, wood) anatomy. Secretory cavities present; with latex. Secondary thickening absent. The axial xylem without vessels.

Root anatomy. Root xylem with vessels; vessel end-walls scalariform and simple (mainly simple).

Reproductive type, pollination. Unisexual flowers absent. Plants hermaphrodite. Floral nectaries present. Nectar secretion from the gynoecium (from the bases and sides of the carpels—corresponding with septal nectaries).

Inflorescence, floral, fruit and seed morphology. Flowers aggregated in ‘inflorescences’; in umbels. The ultimate inflorescence units cymose. Inflorescences scapiflorous; terminal; large, terminal, few-flowered cymose umbels; with involucral bracts (three). Flowers medium-sized (long pedicelled); regular; 3 merous; cyclic; pentacyclic. Floral receptacle not markedly hollowed (convex). Perigone tube absent. Hypogynous disk absent.

Perianth with distinct calyx and corolla (the outer members often tending towards sepaloid), or of ‘tepals’; 6; free; 2 whorled (3+3); isomerous; when not resolvable into calyx and corolla, petaloid; similar in the two whorls to different in the two whorls; green to white, or pink to purple, or brown (white through pink to purplish brown, the outer whorl often tinged with green).

Androecium 9. Androecial members of the outer cycle branched (?—the outer cycle consisting of three pairs of stamens), or unbranched (the inner cycle of three single stamens, these alternating with the outer pairs); free of the perianth; markedly unequal (the three of the inner whorl longer, with markedly longer anthers); free of one another; 2 whorled (6+3). Androecium exclusively of fertile stamens. Stamens 9; triplostemonous; alterniperianthial (i.e. the three pairs of the outer whorl alternating with the inner perianth members). Anthers basifixed; dehiscing via longitudinal slits; latrorse; tetrasporangiate. Endothecium developing fibrous thickenings. The endothecial thickenings spiral. Anther epidermis persistent. Microsporogenesis successive. Anther wall of the ‘monocot’ type. Pollen grains aperturate; 1 aperturate; sulcate; 3-celled.

Gynoecium 6 carpelled (in one whorl). Carpels increased in number relative to the perianth. Gynoecium apocarpous (to carpels basally fused); eu-apocarpous to semicarpous; superior. Carpel incompletely closed (distally unsealed); shortly stylate; apically stigmatic (each style with a ventral, decurrent stigmatic region); 20–100 ovuled (‘many’). Placentation dispersed (the ovules scattered on the sides of the carpel). Stigmas dry type; papillate; Group II type. Ovules over the carpel surface; anatropous; bitegmic; crassinucellate. Embryo-sac development Polygonum-type. Polar nuclei fusing prior to fertilization. Antipodal cells formed, or not formed; when formed, 1, or 2; not proliferating. Synergids hooked (with filiform apparatus). Endosperm formation helobial.

Fruit non-fleshy; an aggregate. The fruiting carpel dehiscent; a follicle. Seeds non-endospermic. Seeds with starch. Cotyledons 1. Embryo achlorophyllous (1/1); straight. Testa without phytomelan; leathery.

Seedling. Germination phanerocotylar. Hypocotyl internode present (long). Seedling collar not conspicuous. Cotyledon hyperphyll elongated; assimilatory; more or less circular in t.s. Coleoptile absent. Seedling macropodous. Seedling cataphylls absent. First leaf dorsiventral. Primary root ephemeral.

Physiology, phytochemistry. Accumulated starch exclusively ‘pteridophyte type’. Not cyanogenic. Alkaloids absent. Saponins/sapogenins absent. Proanthocyanidins absent. Flavonols absent. Ellagic acid absent. Sieve-tube plastids P-type; type II.

Geography, cytology. Holarctic. North temperate. Eurasia. X = 13.

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

Species 1. Genera 1; monogeneric, Butomus.

Economic uses, etc. The rhizomes are edible when baked.

Illustrations. • Le Maout and Decaisne: Butomus. • Butomus umbellatus (B. Ent., 1828).

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: 8th June 2026. delta-intkey.com’.

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