International Aroid Society

30. Syngonium standleyanum Bunting, Baileya 14:21. 1966. TYPE: Costa Rica, Guanacaste, El Arenal, 485-800 m, Standley & Valeria 45248 (US-1254001, holotype).

Juvenile plants with scandent stems, not glaucous; internodes 2.3-6.5 cm long;
petioles sheathed more than 4/5 their length, 4-12 cm long; blades elliptic, in-equilaterally acuminate at the apex, 4-10 cm long, 2-4 cm wide; intermediate leaves elliptic to oblong or lanceolate, subhastate or cordate at the base. Adult plants with stems green, not glaucous, densely and minutely papillate, drying pale brown with longitudinal wrinkles; internodes 3-12 cm long, less than 1 cm diam.; petioles 25-35 cm long, sheathed 2/3 or nearly the full length (1.5-9 cm from the apex), the portion above the sheath acutely angled on the upper side; blades trisect, the leaflets free; median leaflet slightly to very inequilateral, elliptic to oblong, 18-28 cm long, 6.5-12 cm wide, acuminate and mucronate at the apex, acute and attenuate at the base; lateral leaflets elliptic-oblong, 11-24 cm long, slightly if at all more inequilateral than the median leaflet, acute-cuneate on the inner edge at the base, obtuse to rounded or slightly auricled on the outer edge at the base; petiolule 5-15 mm long; primary lateral veins ca. 6 pairs, sunken above, raised beneath; smaller veins clearly visible (at least on drying).
Inflorescences solitary; peduncle 4.5-5.2 cm long, less than 4 cm diam. on drying; spathe 11.5 cm long; spathe tube green, 4.5-5 cm long, ca. 3 cm diam., fusiform-cylin-droid; spathe blade white, ovate-elliptic, 6.2-7 cm long, ca. 2.5 cm diam. (closed), ca. 3.5 cm wide (open), acuminate at the apex, 2.8 cm longer than the spadix;
spadix 8.1 cm long; staminate portion of the spadix clavate, creamy white, ca. 6 cm long.
Infructescences unknown.

DISTRIBUTION: Syngonium standleyanum ranges from Honduras to Costa Rica on the Caribbean slope. In Costa Rica it occurs in tropical wet forest and premontane wet forest at elevations from near sea level to about 500 m.
Bunting (1966) reported that the species could be distinguished by the matte upper blade surfaces, deeply impressed primary lateral veins, and the shape of the leaf blade. In addition the densely papillate stem is characteristic. The species is perhaps closest to S. mauroanum but that species lacks the densely papillate stems, usually has more prominently hastate posterior lobes, and occurs in tropical moist or premontane moist forest.
Birdsey (1955) proposed a new species to be called S. stenophyllum but the name was never published. It was to have been based on Donnell-Smith 6807 (US-936784) and Birdsey 335 (UC, US). I have seen the former and it is S. standleyanum.
COSTA RICA: GUANACASTE: El Arenal, Standley & Valeria 45248 (US); Vicinity of Tilaran, Standley & Valeria 44313 (US). LIMON: La Concepcion, Smith 6807 (US). PUNTARENAS: Osa Peninsula, Parque Corcovado, Ray 3, 17, 18, 19, 44 (GH).
HONDURAS: ZELAYA: In forest behind Bluefields, Bunting & Licht 1250 (K, US).