Pleurothallis mark-wilsonii

Description: — Plant epiphytic, caespitose, medium-sized herb to 17 cm tall. Roots slender, ca. 1.5 mm in diameter. Ramicauls terete, suberect, slender, 3 – 12 cm long, 1.2 – 2.2 mm in diameter, pale green, provided with tubular sheaths, short and truncated up to 2.5 cm long at the base, the bracts brown, papyraceous. Leaf suberect, coriaceous, rigid, sessile, elliptical-ovate, acute, slightly acuminate, 4 – 6 × 2 – 3.5 cm. Inflorescence, a fascicle of single-flowered peduncles, is born from a reclined spathaceous bract, lanceolate, 0.8 mm long, brown, papyraceous and fibrous when mature, eventually dissolving with age. Ovary straight, striate, papillate, 6 – 15 mm long. Flowers beige with vinaceous colored microdots, on the lip the dots are much larger and more visible. Dorsal sepal ovate-lanceolate, concave at the base, very involute forming a tube, acute, long-attenuate, 30 – 35 × 8 – 13 mm, 3 veined. Lateral sepals connate into a narrow ovate-lanceolate synsepal, concave at the base, very involute forming a tail, acute, long-attenuate, 38 – 40 × 6 – 9 mm, 4 veined. Petals oblong-lanceolate, downward inclined, revolute, ciliate, vesiculose to the base, strongly acuminate, 17 – 20 × 2 – 4 mm, 3 veined. Lip triangular, trilobed, curved at the basal part when viewed laterally, irregular, salient margins, acuminate, 3.2 – 3.5 × 2.5 – 2.8 mm, with two diverging keels, elongated, located at the base to near the middle of the lip. Column semiterete, ventrally vesiculose, stigma apical, prominent margins, 2.8 × 1.5 mm. Anther cap broadly ovate, pale yellow, 2 - celled, ca. 0.8 mm long. Pollinia two, narrowly oblong, pyriform, 0.9 mm long, attached to an elliptic viscidium. Fruits not seen.