3. Larrea Cavanilles, Anales Hist. Nat. 2: 119, plates 18, 19. 1800. name conserved.
[For Juan Antonio Pérez Hernández de Larrea, 1730–1803, Catholic bishop of Valladolid, Spain] [For Juan Antonio Pérez Hernández de Larrea, 1730–1803, Catholic bishop of Valladolid, Spain]
Shrubs [prostrate subshrubs]. Stems erect [prostrate], branched, swollen at nodes, quadrangular, becoming cylindric, [less than 1] to 4[–7] m, hairy, becoming glabrate. Leaves opposite, 2-foliolate [even- or odd-pinnately compound]; stipules persistent, herbaceous, ovate [to triangular], apex obtuse to acuminate [apiculate]; petiolules absent; leaflets [1–]2[–17], opposite [alternate], connate basally 2–4 mm (leaves appearing simple and 2-lobed) [distinct], obliquely lanceolate to falcate [oblong to ovate], equal [unequal], base angular, apex mucronate, surfaces appressed-pubescent, becoming glabrate. Pedicels in leaf axils, erect or spreading. Flowers solitary, often irregular by twisting of petals; sepals deciduous, 5, distinct, green, ± unequal, margins undifferentiated, apex obtuse, appressed-pubescent; petals deciduous, 5, imbricate, spreading, twisted, yellow, oblong to oblong-lanceolate [ovate], base clawed, apex obtuse; nectary 10-lobed; stamens 10, ± equal; filaments free, subulate, with ± equal basal scales with toothed [entire] margins; anthers sagittate, versatile; ovary short-stalked, 5-lobed, 5-locular, hirsute-pilose; ovules [6–]8 per locule; style persisting on young fruit, later deciduous, not forming beak; stigma minute. Fruits schizocarps, globose, 5-lobed, splitting septicidally into 5 mericarps. Seeds 1 per locule, brown, boat-shaped. x = 13.
Species 5 (1 in the flora): sw United States, Mexico, South America (Argentina, Bolivia, Chile, Peru); warm desert regions.
SELECTED REFERENCES Campos López, E., T. J. Mabry, and S. Fernández Tavizon. 1979. Larrea. Mexico City. Laport, R. G., R. L. Minckley, and J. Ramsey. 2012. Phylogeny and cytogeography of the North American creosote bush (Larrea tridentata, Zygophyllaceae). Syst. Bot. 37: 153–164. Lia, V. V. et al. 2001. Molecular phylogeny of Larrea and its allies (Zygophyllaceae): Reticulate evolution and the probable time of creosote bush arrival to North America. Molec. Phylogen. Evol. 21: 309–320. Mabry, T. J., J. H. Hunziker, and D. R. DiFeo. 1977. Creosote Bush: Biology and Chemistry of Larrea in New World Deserts. Stroudsburg, Pa.