Arachnothryx darienensis (Standl.) Borhidi

Rondeletia darienensis Standley, sp. nov
Branches slender, terete, brown, loosely arachnoid-tomentose when young; stipules linear-oblong, 3-5 mm. long, obtuse, tomentose or glabrate, erect, persistent; leaves opposite, the petioles slender, 0.6-1.7 cm. long, arachnoid-tomentose when young, the blades elliptic, elliptic-oblong, or oval-oblong, 7-16.5 cm. long, 2.5-7.7 cm. wide, rounded to acutish at the base, short-acuminate at the apex, thin, green above, very thinly arachnoid-tomentose when young but soon glabrate, beneath densely arachnoid-tomentose with grayish hairs, the venation prominent, the lateral veins slender, about 9 on each side, subarcuate; inflorescence terminal, cymose-paniculate, trichotomous, few-flowered, the flowers pedicellate; hypanthium densely tomentose; calyx-lobes 4, lanceolate or narrowly elliptic-oblong, 1-1.5 cm. long, 2.5-4 mm. wide.acute to attenuate, glabrous or nearly so within; corolla in bud about 1.5 cm. long, densely tomentose; capsule subglobose, about 4 mm. long.
Type collected at Boca de Pauarand6. on Sambu River, southern Darien, Panama, altitude 20 meters, February, 1912, H. Pittier 5684 (U. S. Nat. Herb. no. 867136).

Arachnothryx darienensis là một loài thực vật có hoa trong họ Thiến thảo. Loài này được (Standl.) Borhidi mô tả khoa học đầu tiên năm 1982.