Thryallis L., Sp. Pl. (ed. 2) 554. 1762, non Thryallis Mart., 1829, nom. cons.—Type: T. brasiliensis L. [G. brasiliensis (L.) Adr. Juss.].
Shrubs or subshrubs, occasionally small trees; stipules intrapetiolar, distinct, persistent on stem; leaves usually bearing glands on petiole and/or proximally on margin of lamina. Inflorescence terminal, erect, a pseudoraceme of single flowers [1-flowered cincinni], the pseudoracemes single or several grouped in a panicle; floriferous peduncles developed or very short to absent; bracteoles eglandular, long-persistent, mostly borne below apex of peduncle when peduncle is developed. Sepals leaving outermost petals exposed in enlarging bud, all eglandular or with a single very small gland at base of sinus between some or all adjacent sepals; corolla varying from moderately bilaterally symmetrical to nearly radial, the posterior petal then hardly different from the lateral 4; petals bright yellow, often suffused with red or turning red in age, glabrous or sparsely hairy on abaxial midrib, minutely denticulate or slightly erose; androecium mostly bilaterally symmetrical, rarely radial; stamens glabrous; filaments distinct or connate at base, mostly longer opposite sepals than opposite petals; anthers subequal; pollen 3 (–4)-colporate with colpi branching and fusing (parasyncolporate) in some spp.; receptacle glabrous; gynoecium radially symmetrical; ovary with the carpels 3, connate along a broad adaxial face; styles 3, slender and subulate with minute stigmas. Cocci 3, leaving little or no raised torus, ± smooth except for a narrow dorsal keel. Chromosome numbers: n = 6, 12 (W. R. Anderson, 1993a).
A genus of 26 species, four South American [map], the rest North American [map], the latter mostly Mexican but extending as far north as Texas (G. angustifolia) and as far south as Nicaragua (G. speciosa). Most species are found in seasonally dry, open habitats, but some Mexican species occur in more mesic woodlands, and one grows on dunes of the Pacific coast. Earlier publications used the name Thryallis L. for this genus, and that usage persists in some herbaria and, especially, in the horticultural trade, but the later name Thryallis Mart. has been conserved for a different genus of Brazilian Malpighiaceae, so the Linnaean name cannot be used for this genus. — Regional keys to genera: USA, Caribbean, Central America.
Galphimia resembles its sister Verrucularia in several characters, most notably its distinct stipules, eglandular bracteoles, and glabrous receptacle. It differs in the marginal leaf glands, the cincinni always reduced to one flower, the anther locules without lateral outgrowths, and the calyx glands absent or represented by up to five tiny glands that occur singly just below the sinus between adjacent sepals. Accompanying the loss of calyx glands there has been a shift in some species toward large anthers and nearly radial flowers; the pollinators are probably pollen-collecting bees, not the oil bees that pollinate most neotropical Malpighiaceae.
Uses: One species native in eastern Mexico, Galphimia gracilis Bartl., is widely cultivated in the tropics and subtropics as an ornamental shrub. It passes under the colloquial names "goldshower" and "shower-of-gold" and equivalents in local languages, and also as "thryallis." It is frequently misidentified as "Galphimia brasiliensis," "Galphimia glauca," "Thryallis brasiliensis," T. glauca," and "Thryallis gracilis."
Galphimia gracilis is easily told apart from the true G. glauca and G. brasiliensis by the flowers. In G. gracilis the petals fall as the fruit matures; in G. glauca the petals are persistent even in fruit. In G. gracilis many flowers of a dense inflorescence are open at one time, and the petals (claw and limb) are 8–14 mm long and 4–8 mm wide; in G. brasiliensis only 2 or 3 small flowers are open at one time on a sparse inflorescence, and the petals are only 4–5 mm long and ca. 3 mm wide. Galphimia glauca and G. brasiliensis are not cultivated.
Drawings: view all; (those most representative of the genus in boldface): G. amambayensis, G. angustifolia, G. arenicola, G. australis, G. brasiliensis, G. calliantha, G. elegans, G. floribunda, G. glandulosa, G. glauca, G. gracilis, G. grandiflora, G. langlassei, G. mexiae, G. mirandae, G. multicaulis, G. oaxacana, G. paniculata, G. platyphylla, G. radialis, G. sessilifolia, G. speciosa, G. tuberculata, G. vestita.