1. Fagonia Linnaeus, Sp. Pl. 1: 386. 1753; Gen. Pl. ed. 5, 182. 1754.
[For Guy-Crescent Fagon, 1638–1718, French botanist and chemist, physician to Louis XIV] [For Guy-Crescent Fagon, 1638–1718, French botanist and chemist, physician to Louis XIV]
Herbs, subshrubs, or shrubs, perennial. Stems erect to spreading or ± prostrate, highly branched, angled or ridged [terete], less than 1 m, becoming woody at least at base, hairy and glandular to almost glabrate [glabrous]. Leaves opposite, palmately compound [rarely scalelike]; stipules persistent, stiff [herbaceous], spinelike, apex spinose or spinulose; petiolules usually present; leaflets (1–)3[–7], inserted on petiole apex, distinct, [linear] lanceolate to ovate [obovate], terminal largest, base cuneate, apex spinose, surfaces stipitate-glandular, glabrate, or glabrous [hairy]. Pedicels in leaf axils, erect, becoming reflexed in fruit. Flowers usually solitary, regular to slightly irregular by twisting of petals; sepals deciduous or persistent, 5, distinct, green to purple, equal, margins undifferentiated or sometimes membranous, apex acute-attenuate, hairy or glandular to glabrate [glabrous]; petals soon deciduous, 5, imbricate, spreading, often twisted (propellerlike), purple to pink [rarely white], ± obovate, base clawed, apex rounded, usually apiculate; nectary rudimentary; stamens 10, ± equal; filaments free, filiform, unappendaged; anthers sagittate; ovary sessile, 5-lobed, 5-locular, hairy and usually glandular; ovules (1–)2 per locule; style persistent, forming beak on fruit; stigma minute. Fruits capsules, ovoid, deeply 5-lobed, loculicidally dehiscent. Seeds usually 1 per locule, brownish to black, flat, ± ovate, seed coat mucilaginous when wet.
Species 35 (3 in the flora): sw United States, nw Mexico, sw South America, w, s Asia, n, sw Africa, Atlantic Islands (Canary Islands, Cape Verde Islands); warm-arid habitats.
Although Fagonia species are perennial, they sometimes facultatively form flowers and reproduce during their first season. The seeds of Fagonia are sticky when wet, which probably aids in dispersal (D. M. Porter 1974b).
Although Fagonia laevis and F. pachyacantha do not cluster next to one another in the trees illustrating a phylogenetic study of the genus (B.-A. Beier et al. 2004b), they were placed together in the taxonomic revision (Beier 2005). Beier reported F. californica Bentham from Arizona and California, considering F. laevis and F. longipes to be synonyms; however, F. californica is a species of Baja California Sur and Sonora and does not occur in the flora area (D. M. Porter 1963). Fagonia californica differs from F. longipes in being prostrate-spreading, not erect to spreading; having leaflets that are elliptic to oblong-lanceolate or oblong, not linear to linear-lanceolate; and having pedicels that are stout and 1–6 mm, not slender and 8–20 mm. It differs from F. laevis, which has erect to spreading stems and linear-elliptic leaflets and is mostly glabrous, not densely stipitate-glandular.
SELECTED REFERENCES Beier, B.-A. 2005. A revision of Fagonia (Zygophyllaceae). Syst. Biodivers. 3: 221–263. Beier, B.-A. et al. 2004b. Phylogenetic relationships and biogeography of the desert plant genus Fagonia (Zygophyllaceae), inferred by parsimony and Bayesian model averaging. Molec. Phylogen. Evol. 33: 91–108.