Triopterys L., Sp. Pl. 428. 1753.—Type: T. jamaicensis L. [M. lucida (H. B. K.) W. R. Anderson & C. Davis].
Twining vines with woody stems varying from slender to stout, occasionally described as shrubby; stipules interpetiolar (borne on stem beside petioles), small, distinct and triangular or rarely connate in interpetiolar pairs; leaves decussate; petiole eglandular or biglandular at base or between base and apex; lamina in most species bearing glands embedded in abaxial surface. Inflorescences elongated or occasionally congested pseudoracemes, single or grouped in panicles; bracts eglandular, persistent; bracteoles eglandular or one of each pair bearing one abaxial gland, persistent, borne at various heights on the well-developed peduncle. Flowers bilaterally symmetrical in all whorls, bisexual. Sepals leaving petals exposed in enlarging bud, the lateral 4 bearing large paired abaxial glands and the anterior eglandular; petals yellow, pink, white, or various shades of lilac, blue, or purple, glabrous, entire, erose, or dentate, the posterior petal somewhat different in size, shape, and stance from the lateral 4; receptacle glabrous on both sides of filaments; stamens 10, all fertile, the filaments glabrous, connate at base, shortest opposite posterior petal, otherwise diverse but not rarely thicker opposite posterior-lateral petals, the anthers glabrous or hairy, ± alike, the connective not exceeding locules at apex; gynoecium 3-carpellate, the carpels 1 anterior and 2 posterior, all fertile, connate their whole length in ovary; styles 3, distinct, alike or the anterior style shorter than the posterior 2, abaxially rounded, truncate, or short-hooked at apex, stigmatic on internal angle of apex. Fruit dry, breaking apart at maturity into 3 samaras separating from a pyramidal torus; samara mostly elliptical or orbicular (occasionally triangular) with the lateral wing well developed, membranous with a prominent reticulum of arching anastomoses, in most species continuous at base (divided to the nut in a few species) and entire to deeply cleft at the apex, in a few species strongly reduced or dissected, in a few species indented at the sides and Y-shaped (“Triopterys”), the dorsal crest or winglet very small or absent; fruit subtended by a fleshy 3-lobed disc, the disc sometimes much reduced; carpophore absent. Chromosome numbers: n = 10 (M. polybotrya), n = 20 (M. cordifolia) (W. R. Anderson, 1993a); photo.
A New World genus of approximately 45 species, occurring from northern Mexico to northern Argentina and southeastern Brazil and in the Caribbean [map], growing in diverse habitats. — Regional keys to genera: Caribbean, Central America.
Mascagnia in the traditional sense of Niedenzu (1928) and later authors was a highly polyphyletic assemblage (see discussion by W. Anderson, 2006b [pdf]); it was a form-genus based solely on the lateral-winged samaras. After the removal of discordant elements over the last three decades Mascagnia was monophyletic, except that the small Caribbean genus Triopterys was found to be nested within Mascagnia (Davis & Anderson, 2010 [pdf]). Those two genera have now been combined, and Mascagnia is now monophyletic with 86 bootstrap percentage support (Anderson & Davis, 2013 [pdf]). Because Triopterys is an older name than Mascagnia, a proposal has been submitted for the conservation of Mascagnia against Triopterys (Anderson & Davis, 2012 [pdf]).
Species of Mascagnia are twining woody vines (sometimes said to be shrubby), but two species, M. almedae and M. vacciniifolia, also climb by means of rootlets arising from the stem (photo). The genus is characterized by distinct interpetiolar stipules and (in most species) glands embedded in the abaxial surface of the lamina (never on the margin). The flowers, each borne on a pedicel subtended by a well-developed peduncle, are arranged in pseudoracemes (never in a 4-flowered umbel). Petal color varies from yellow, pink, white, to various shades of blue or lilac (the last colors otherwise rare in the family). In most species the samara has a veiny, membranous, elliptical or orbicular (occasionally triangular) lateral wing and sometimes a dorsal crest or winglet. The high pyramidal torus is subtended by a fleshy three-lobed disc (sometime much reduced), which is apparent only after the samara have fallen.
References: There is no modern revision of the genus, and the treatment by Niedenzu (1928) is difficult to use because of his broad taxonomic concept of this genus. The discordant elements were removed by Johnson (1986 [pdf]: Callaeum), Anderson & Davis (2005b: Malpighia leticiana; 2007: Calcicola), W. R. Anderson (2006b [pdf]: Adelphia, Aenigmatanthera, Alicia, Amorimia, Carolus, Christianella, Malpighiodes, Niedenzuella), and Anderson & Corso (2007: Psychopterys). Anderson & Davis revised the Mascagnia cordifolia group (2005a) and combined Mascagnia and Triopterys (2013 [pdf]). See also descriptions of new species by C. Anderson (2001c [pdf]) and W. R. Anderson (1980b, 1997b, 2007b) and floristic treatments by W. R. Anderson (1981b [pdf 20 MB], 2001a [pdf], 2001e [pdf], 2002 [pdf], 2007c [pdf]).
Drawings: M. aequatorialis, M. allopterys, M. almedae, M. aptera, M. arenicola, M. australis, M. boliviana, M. brevifolia, M. cordifolia, M. corymbosa, M. divaricata, M. lilacina, M. lucida, M. riparia, M. schunkei, M. tomentosa, M. tucuruensis, M. vacciniifolia, M. velutina, M. violacea