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The families of flowering plants.                                                                                                                                                                

Loasaceae Spreng.

                        

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IncludingCevalliaceae Griseb., Gronoviaceae Endlicher

Habit and leaf form. Small trees (rarely), or shrubs (sometimes), or herbs (mostly, mostly bristly); non-laticiferous and without coloured juice. Plants non-succulent. Annual, or perennial (more often). Self supporting, or climbing; sometimes herbaceous stem twiners; twining clockwise (Scyphanthus), or twining clockwise and twining anticlockwise (variable, Loasa). Leaves alternate, or opposite; long petiolate to sessile; not gland-dotted; simple. Lamina dissected, or entire; when dissected, variously pinnatifid, or palmatifid, or much-divided; pinnately veined, or palmately veined; cross-venulate. Leavesexstipulate (at least mostly).

General anatomy. Plantswithout laticifers.

Leaf anatomy. Stomata present; anomocytic. Hairs present (coarse, silicified and often calcified); eglandular, or glandular. Urticating hairs present, or absent.

Laminamostly isobilateral, or centric. Cystoliths present (commonly, at the bases of hairs), or absent. Minor leaf veins without phloem transfer cells (Blumenbachia).

Stem anatomy. Primary vascular tissue centrifugal. Secondary thickening absent, or developing from a conventional cambial ring. Xylem with fibre tracheids. Vessel end-walls simple. Wood partially storied (VI).

Reproductive type, pollination. Fertile flowershermaphrodite. Unisexual flowers absent. Plants hermaphrodite. Floral nectaries present, or absent (?). Nectar secretion from the androecium (from staminodes).

Inflorescence, floral, fruit and seed morphology. Flowers solitary, or aggregated in ‘inflorescences’ (more often). The ultimate inflorescence unit cymose. Flowers regular; cyclic. Floral receptacle markedly hollowed. Free hypanthium present (‘the petals inserted on the calyx’).

Perianthwith distinct calyx and corolla; (8–)10(–14); 2 whorled; isomerous. Calyx (4–)5(–7); polysepalous; regular; persistent; imbricate, or contorted.Corolla (4–)5(–7) (or 10 when supplemented by petaloid staminodes); polypetalous, or gamopetalous; induplicate valvate; yellow (usually), or white (rarely), or red (rarely). Petals clawed, or sessile.

Androecium 5 (Gronovioideae), or 10–100 (usually ‘many’). Androecial members branched (sometimes, in antepetalous bundles), or unbranched; when determinable, maturing centripetally (Mentzelioideae), or maturing centrifugally (Loasoideae); free of the perianth, or adnate (sometimes with nearly sessile anthers borne on the corolla tube); free of one another, or coherent (sometimes basally connate into a short tube, or into antepetalous bundles). The androecial bundles when bundled, opposite the corolla members. Androecium exclusively of fertile stamens, or including staminodes (often). Staminodes petaloid (sometimes), or non-petaloid, or petaloid and non-petaloid (and sometimes nectariferous, sometimes as in Loasa and Blumenbachia, three or more of them being united to form a large, coloured nectary whose mouth is towards the centre of the flower and is partly obstructed by the other staminodes). Stamens 5, or 10–100 (to ‘many’); reduced in number relative to the adjacent perianth to polystemonous. Anthers dehiscing via longitudinal slits; tetrasporangiate. Pollen shed as single grains. Pollen grains aperturate; 3 aperturate; colporate; 2-celled.

Gynoecium1 carpelled (ostensibly, in Grovonoideae), or 3–5(–7) carpelled. The pistil 1 celled, or 2 celled, or 3–7 celled (rarely). Gynoecium syncarpous (but with pseudomonomery in the Gronovioideae); synstylovarious to eu-syncarpous; partly inferior to inferior (often ribbed, the ribs sometimes spiralled). Ovary 1 locular (usually, often with more or less deeply intruded placentas, and pseudomonomerous in Gronovioideae), or 2 locular (rarely, fully partitioned). Gynoecium stylate. Styles 1; apical. Stigmas dorsal to the carpels. Placentation when unilocular, parietal (usually), or apical (pseudomonomerous Gronovioideae); when plurilocular, i.e. rarely, axile. Ovules in the single cavity 1–100 (to ‘many’); 1–50 per locule (to ‘many’); non-arillate; anatropous, or hemianatropous; unitegmic; tenuinucellate. Endothelium differentiated. Embryo-sac development Polygonum-type. Antipodal cells formed; 3; not proliferating; persistent (in a shallow pouch). Endosperm formation cellular (with chalazal and micropylar haustoria). Endosperm haustoria present; chalazal and micropylar. Embryogeny solanad.

Fruit non-fleshy; dehiscent (usually), or indehiscent; a capsule (usually, straight or spirally twisted), or capsular-indehiscent, or achene-like, or a nut. Capsules usually septicidal, or loculicidal. Seeds copiously endospermic (usually), or non-endospermic (endosperm scanty or wanting in Gronovioideae). Endosperm oily. Embryo well differentiated. Cotyledons 2; flat. Embryo achlorophyllous (1/1); straight, or curved (spathulate).

Seedling.Germination phanerocotylar.

Physiology, biochemistry. Not cyanogenic. Alkaloids absent (3 species). Iridoids commonly detected; ‘Route I’ type (normal and seco). Proanthocyanidins absent. Flavonols present; kaempferol, or quercetin. Ellagic acid absent (2 genera, 2 species). Saponins/sapogenins absent. Aluminium accumulation not found. C3. C3 physiology recorded directly in Petalonyx.

Geography, cytology. Holarctic, Paleotropical, and Neotropical. African. Temperate to tropical. Mostly tropical or subtropical, southern U.S.A., Central and South America, with only Fissenia (Kissenia) in Arabia and Southwest Africa. X = 7–15(+).

Taxonomy.Subclass Dicotyledonae; Tenuinucelli. Dahlgren’s Superorder Loasiflorae; Loasales. Cronquist’s Subclass Dilleniidae; Violales. APG 3 core angiosperms; core eudicot; Superorder Asteranae; Order Cornales.

Species 250. Genera 14; Blumenbachia, Caiophora, Cevallia, Eucnide,Fissenia, Fuertesia, Gronovia, Klaprothia, Loasa,Mentzelia, Petalonyx, Plakothira, Schismocarpus, Scyphanthus.

 Illustrations:

  • Technical details: Caiophora, Loasa.
  • Technical details: Bartonia (= Mentzelia).
  • Technical details: Mentzelia (Lindley).
  • Blumenbachia lateritia: as Loasa, Bot. Reg. XXIV, 22 (1838).
  • Loasa acanthifolia: Bot. Reg. 785, 1824.
  • Loasa ambrosiaefolia: Bot. Reg. 1390, 1830.
  •  Mentzelia lindleyi: as Bartonia aurea, Bot. Reg 1831 (1836).
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