Oreopanax arcanus A. C. Sm.

Oreopanax arcanus A. C. Smith, sp. nov.*
Shrub about 8 m. high, or smaller and epiphytic, the branchlets stout, sparsely stellatetomentellose or glabrous; leaves simple, the petioles stout, striate, (2-) 4-17 cm. long, glabrate, the blades papyraceous to subcoriaceous, ovate, 13-25 cm. long, 6-13 cm. broad, broadly obtuse to subcordate at the base, cuspidate or short-acuminate at the apex, entire and narrowly recurved at the margins, smooth on both surfaces, sparsely pilose beneath with short-stalked stellate 4-6-branched hairs, sometimes scattered-pilose above, the primary nerves 5, spreading from near the base, raised on both surfaces (or the outer pair faint), the costa with several pairs of spreading arcuate lateral nerves, the veinlets usually immersed; staminate inflorescence not seen; hermaphrodite inflorescence compactly paniculate, 5-7 cm. long and broad, the branches and peduncles tomentellose with pale stellate sessile or subsessile 4— 6-branched hairs, the bracts subtending principal branches subfoliaceous in texture, lanceolate, 15-30 mm. long, the bracts subtending peduncles subcoriaceous, oblong-subulate, 2-5 mm. long, the peduncles stout, 9-13 mm. long; hermaphrodite heads subglobose, 5-7 mm. in diameter, composed of 2 or 3 flowers completely enclosed by the papyraceous strongly concave bracts and bracteoles; outer bracts of the head 2 or 3, broadly ovate, 2-3 mm. long, 5-6 mm. broad, obscurely apiculate at the apex, ciliolate at the margins, otherwise glabrous, the bracteoles 2 subtending and surrounding each flower, similar to the outer bracts but slightly smaller; flowers subglobose, about 2.5 mm. in diameter just before anthesis, the calyx strongly urceolate, carnose, truncate at the apex; petals usually 5, sometimes 4 or 6, membranous, deltoid, subcoherent in a small calyptra about 1.7 mm. across; stamens usually 5, the filaments minute, the anthers oblong, about 0.8 mm. long; styles usually 5, stout, about 0.5 mm. long, free to the base.
Type: Guatemala, Dept. Huehuetenango, Cerro Pixpix, above San Ildefonso Ixtahuacan, alt. 1600-2800 m., Steyermark 50645, Aug. 15, 1942 (in herb. Arnold Arb.).
Distribution: Guatemala, known from the type collection and from Steyermark 50025, Dept. Huehuetenango, above San Juan Ixcoy, Sierra de los Cuchumatanes, alt. 2400 m.
* Oreopanax arcanus, sp. nov.; frutex, foliis ovatis, ad apicem cuspidatis vel acuminatis, subtus sparse stellato-tomentellis; innorescentiis hermaphroditis compactis paniculatis, ramis a bracteis lanceolatis subfoliaceis subtentis, capitulis 2vel 3-floris, floribus bracteis bracteolisque imbricatis arcanis; calyce urceolato truncato; petalis parvis in corolla calyptrata subconnatis; stylis liberis; L. fiaccido Marchal affinis, tomento sparsiore, inflorescentia compacta, bracteis bracteolisque flores complectentibus differt.

Oreopanax arcanus is a species of plant in the family Araliaceae. It is found in Guatemala and Mexico. It is threatened by habitat loss.