Encyclia ambigua (Lindley, 1853) Schlechter, 1914

Carnevali, Germán, Pérez-García, Eduardo A., Leopardi-Verde, Carlos Luis, Tapia-Muñoz, José Luis, Cetzal-Ix, William R., Ramírez-Morillo, Ivón M. & Romero-González, Gustavo A., 2018, The Encyclia ambigua complex (Laeliinae, Orchidaceae), a synopsis and notes on Encyclia virens and Epidendrum alatum, Phytotaxa 372 (1), pp. 1-21 : 15

Key to the species of the Encyclia ambigua complex

1. Petals narrowly elliptic, slightly (if at all) clawed, claw at 45° relative to the dorsal sepal, petal blade at the same angle or slightly bent to up to 60°, 27.5–29 × 7.5–9 mm; the nerves of the lip slightly elevated; column subapically with small, triangular, acute stelidia; inflorescences 70–100 (–150) cm long; pedicellate ovary 30–33 mm long; flowers ca. 50 mm diameter; sepals 27.5–32 × 6–7.5 mm; petals and sepals pale green to straw-white, the claw concolorous; lip white (rarely pale yellow), with 7–11 purple, continuous nerves that reach half the length of the midlobe, the rest of the midlobe may or may not have fine broken purple lines or spots approaching the midlobe margin; column green to straw-white; plants from the highlands of Chiapas in Mexico and, probably, neighboring Guatemala............................................................................................................................................. E. ambigua

– Petals in overall outline oblanceolate, strongly clawed, claw 45°–70° relative to the dorsal sepal, petal blade almost (75–90°) perpendicular to the dorsal sepal, 15–17 × 5–6 mm; the nerves of the lip always strongly elevated and scabrous or crisp; column subapically with a pair of subquadrate, truncate stelidia; inflorescences 80–105 cm long; pedicellate ovary 18–26 mm long; flowers ca. 35–37 mm diameter; sepals 16–20 × 5–7 mm; petals and sepals yellow or green yellow, brown or maroon suffused, the colors of several hues but always richly colored, the claw contrasting green; lip yellow with many minute broken lines or spots that always reach the central lobe margin, no continuously colored nerves; column yellow; plants from the western section of the Chiapas Highlands in Mexico or from Guatemala east of the Cordillera de los Chuchumatanes, Honduras, El Salvador, and northern Nicaragua......................................................................................................................................................................................2

2. Midlobe of the lip subquadrate to broadly oblong-subquadrangular (15–21 mm long, 10–12(–15) mm across the forcefully expanded lateral lobes), apically truncate, rounded to emarginate, sessile with the callus contained in the proximal portion of the central lobe; petals with a narrow claw, the blade about as wide as long; plants from eastern Guatemala, Honduras, El Salvador, and northern Nicaragua................................................................................................................................................. E. trachychila

– Midlobe narrowly ovate to narrowly elliptic (13–15 mm long, 7–9 mm across the forcefully expanded lateral lobes), acute, conspicuously longer than wide, strongly clawed with the claw formed by the strongly elevated distal portion of the callus; petals clawed, the blade longer than wide; plants from western Chiapas in Mexico ................................................................. E. dressleri .