Loasaceae Juss.

Milliken, W., Klitgard, B. and Baracat, A. (2009 onwards), Neotropikey - Interactive key and information resources for flowering plants of the Neotropics. http://creativecommons.org/licenses/by/3.0

Morphology General Habit

Usually annual, biennial or perennial herbs, sometimes winding, rarely subshrubs, very rarely woody lianas or cushion-forming plants, thickend storage roots sometimes present

Morphology Leaves

Leaves usually opposite below and alternate above, rarely opposite or alternate throughout, simple or compound, mostly widely ovate with lobed margin, lobes lobulate and serrate, sometimes pinnate or bipinnate or palmatifid, very rarely cordate with acuminate tip and entire margin or linear, or lyrate with undulate or pinnatifid /-sect margin; estipulate but pseudostipules rarely present

Morphology Reproductive morphology Inflorescences

Inflorescences terminal, thyrsoids, rarely monochasial or dichasial cymoids, sometimes apparently single and axillary, very rarely in racemes or in heads; inflorescence bracteose or frondose, very rarely ebracteose

Morphology Reproductive morphology Flowers

Flowers hermaphrodite, (4-)5(-8)- merous, actinomorphic or very weakly zygomorphic; sepals well developed, sometimes larger than petal, entire or dentate, sometimes pinnate; petals often white, or yellow, orange, pink, red, sometimes two-coloured; stamens 5-10-40-100-150, antesepalous, obdiplostemonous, or polyandrous, then often outer ones with dilated filaments or petaloid, or fertile antepetalous fascicles with stamens reflexed into petals alternating with antesepalous staminodial groups, these often (subfam. Loasoideae) modified into staminodial complexes (typically 3 outer ones fused into floral scale, 2 inner ones free but closing the adaxial side of the scale), floral scale extremely variable in size, shape, ornamentation and colouration, ofter 2-3-coloured; ovary syncarpous, hypogynous, of 3--5 carpels, unilocular, single style with very long but nearly or completely coherent stigmatic lobes

Morphology Reproductive morphology Flowers Nectaries

Nectary disc absent or present and cup-shaped, or nectaries in 5 antesepalous bulges

Morphology Reproductive morphology Fruits

Fruit crowned with persistent, sometimes accrescent calyx, sometimes single-seeded and indehiscent, usually a many-seeded capsule opening with 3-5 apical valves, or with 3-10 longitudinal slits, seeds 1-3,000, rarely smooth, usually with at least reticulate testa, often with complex honeycomb pattern, or lateral or terminal wings.

Note

Number of genera: Twenty Neotropical genera.  Subfamily Loasoideae comprises ca. 200 species and thus nearly 2/3rds of the species of the family. Ca. 190 of these are South American. The family is a potential source of highly unsaturated oils from the seeds. Several species are used in traditional medicine, but only one is found in international trade and only to a very limited extent (Mentzeliascabra subsp. chilensis (Gay) Weigend). Many species, especially in Aosa, Nasa, Caiophora and Loasa, have extremely painful stinging hairs. A large number of species, especially of the genus Nasa, are very narrowly endemic, some only known from the type collection, and at least 2 already extinct (N. hastata (Killip) Weigend from C Peru and N. humboldtiana subsp. humboldtiana (Urb. & Gilg) Weigend from S Ecuador). Members of the Loasaceae represent a well-supported monophylum, in spite of their wide variability in most morphological characters. Its closest ally is Hydrangeaceae, with some striking morphological similarities (flower, fruit, seed and leaf) between genera such as Deutzia Thunb., Philadelphus L. and Jamesia Torr. & A.Gray of that family and Klaprothieae of Loasaceae.

Diagnostic

Nasa: monochasia with a single bract per flower, strongly urticant. Caiophora: fruits opening with longitudinal slits, strongly urticant. Scyphanthus: fruits linear, not urticant. Blumenbachia: all fruits twisted in the same direction (anticlockwise), all leaves opposite. Eucnide: flower polyandrous and filaments basally fused with corolla, staminodia absent, plants urticant. Schismocarpus: obdiplostemonous, narrowly endemic in S Mexico. Petalonyx: inflorescence racemose, filaments inserted between petals or apparently outside petals. Gronovia: haplostemonous, winding and urticant with deeply lobed leaves. Fuertesia: haplostemonous, woodyliana with cordate, entire, coriaceous leaves. Klaprothia: flowers tetramerous, white, antesepalous staminodia free, yellow, common weed. Xylopodia: flowers tetramerous, green, antesepalous staminodia united into green floral scale with yellow apex, very narrowly endemic in Prov. Contumazá, N Peru. Key differences from similar families: Members of the Loasaceae are sometimes confused with Cucurbitaceae or Malvaceae:  Flowers hermaphrodite (vs. usually unisexual in Cucurbitaceae). Leaves estipulate (stipulate in Malvaceae). Pubescence of glochidiate/scabrid trichomes (stellate trichomes in Malvaceae) Distinguishing characters (always present): Predominantly herbs with scabrid or glochidiateindumentum. Stinging hairs often present. Inferior ovary with 3--5 carpels and intrusive-parietal placentation. Single style with very short, stigmatic lobes or without. Fruits mostly capsules opening with apical valves.

Distribution

All species are native, and many species are very narrowly endemic. Mentzeliaaspera Vell. is likely to have originated in N Central America and has probably been spread as a weed. Loasaceae comprise 20 genera and over 300 species. Virtually all of them belong to the New World and ca. 200 species are found in the Neotropics. Only the genera Kissenia R.Br. ex T.Anderson (Africa, Arabia) and Plakothira J.Florence (Polynesia) are extra-American. 50 genera and 500 species occur in the Neotropics. Representation of genera: Aosa Weigend (7 species) Brazil, Hispaniola. Blumenbachia Schrad. (12 species) Brazil, Uruguay, Paraguay, Argentina, Chile. Caiophora C.Presl (ca. 50 species) Peru, Bolivia, Argentina, Chile, Uruguay, Brazil, Ecuador. Cevallia Lag. (1 species) SW USA and N Mexico. Chichicaste Weigend (1 species) NW Colombia to Costa Rica. Eucnide Zucc. (13 species), Guatemala, Mexico to SW USA. Fuertesia Urb. (1 species) Hispaniola. Gronovia L. (2 species) NW Peru to Mexico. Huidobria Gay (2 species) Chile. Klaprothia Kunth (2 species) S Mexico to Brazil and Bolivia, also Caribbean, Galapagos. Loasa Adans. (36 species) Chile, Argentina, Peru. Mentzelia L. (80 species) Argentina to Canada, Caribbean and Galapagos Is., most SW USA and Mexico. Nasa Weigend (100 species) Colombia, Ecuador, Peru, Chile, Bolivia, Venezuela, C America to S Mexico. Petalonyx A.Gray (5 species) N Mexico and SW USA. Presliophytum (Urb. & Gilg) Weigend (3 species) Peru. Schismocarpus S.F.Blake (1 species) Mexico. Scyphanthus D.Don (1-2 species) Chile. Xylopodia Weigend (1 species) Peru.