Family Butomaceae

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). Accumulated starch exclusively ‘pteridophyte type’.

Leaf anatomy. Stomata present; paracytic. Guard-cells not ‘grass type’.

Lamina with secretory cavities. Secretory cavities containing latex; schizogenous. The mesophyll containing calcium oxalate crystals, or without calcium oxalate crystals (? — no raphides). Vessels absent.

Stem anatomy. Secretory cavities present; with latex. 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).

Reproductive type, pollination. 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 unit 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, biochemistry. Not cyanogenic. Alkaloids absent. Proanthocyanidins absent. Flavonols absent. Ellagic acid absent. Saponins/sapogenins absent.

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

Taxonomy. Subclass Monocotyledonae. Dahlgren et al. Superorder Alismatiflorae; Hydrocharitales. APG 3 core angiosperms; Superorder Lilianae; non-commelinid Monocot; Order Alismatales.

Species 1. Genera 1; monogeneric, Butomus.

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

Illustrations.
• Technical details: Butomus.
• Butomus umbellatus (B. Ent.).