Prescottia ostenii Pabst

Azevedo, Cecília Oliveira De, Berg, Cássio Van Den & Barros, Fábio De, 2014, A revision of Prescottia (Orchidaceae: Orchidoideae, Cranichideae), Phytotaxa 178 (4), pp. 233-286 : 267

11. Prescottia ostenii Pabst , Bradea 3: 19. 1979. [ Pabst 1980, Azevedo & van den Berg 2007a, Singer et al. 2009].

Type:— URUGUAY. Canelones: La Floresta, 23 October 1933, Osten 22939 (lectotype S!, isolectotypes MVFA!, MVM!, selected by Azevedo & Van den Berg 2007a). Fig. 26 .

Terrestrial herbs. Leaves (1–)2–5, rosulate, sessile; blade green, (0.8–)2.0–4.0(–5.0) × 1.0– 1.5 cm, elliptic to ovate, apex acute, base rounded, margin entire. Inflorescence 9–20-flowered; peduncle green, (1.5–)4.0–4.5 × 0.2–0.3 cm, cylindric; peduncle bracts green, 1–4, 3.0–8.0(–11.5) × (1.0–)3.0–4.0(–6.0) mm, ovate, apex acute; rachis green 1.0– 2.0 × 0.5–0.7 cm. Flower bracts green, 2.0–5.0 × 1.5–2.5 mm, ovate, apex acuminate; flower erect, white, dorsal sepal revolute, 1.0–1.3 × 1.0– 1.3 mm, ovate, apex acute; lateral sepals adpressed to the lip to patent, 1.3–1.5 × 1.3–1.5 mm, ovate, apex obtuse; petals revolute, 1.0–1.3 × 0.3–0.5 mm, oblong, apex obtuse; lip 1.5–1.7 × 1.0– 1.5 mm, inner surface pubescent, outer surface densely minute-papillose. Column at least 0.5 mm long, glabrous.

Distribution:— Brazil and Uruguay ( Fig. 17 ).

Selected Specimens Examined:— BRAZIL. Rio Grande do Sul: Tramandaí, Jardim do Éden , 18 August 2007, Singer 2006 50 ( ICN) .

Habitat:— Prescottia ostenii has always been reported from moist, humid places, with its roots in water. It has been found among marshy, paludicolous open vegetation in full-sun near to the Atlantic Coast.

Conservation Status:— Critically endangered ( CR – A1 a). Prescottia ostenii is known only from the type locality and two additional collections. In Brazil, it was collected for the first time after more than 70 year from the last collection in Uruguay, and apparently it has not been collected there since ( Singer et al. 2009) .

Etymology:— In honor of Dr. Cornelius Osten, German botanist and businessman in Uruguay, who made the original collection.

Notes:— Prescottia ostenii is a poorly known species, but it is easily recognized by its habit (it is only 5–8 cm tall when in flower) and dense inflorescence. Morphologically, this species is similar to P. densiflora because both share sessile rosulate leaves, but it differs conspicuously in plant size (it is much shorter).

Charles Schweinfurth recognized this material to be a new species of Prescottia in 1934. He wrote a note on the material at GH but never described it. Prescottia ostenii was described by Pabst (1979) from specimens collected at Canelones, Uruguay. It was recently recorded for Brazil ( Singer et al. 2009). At present, it was only known from two sites, one each in Brazil and Uruguay.

Figures

FIGURE 17. Distribution of Prescottia glazioviana, P. leptostachya, P. mucugensis, P. ostenii, P. phleoides and P. spiranthophylla.

FIGURE 26. Prescottia ostenii. Drawn from fresh material.A. Habit. B. Detail of inflorescence. C. Flower, front view. D. Floral bract. E. Perianth parts, clockwise from top: lip, lateral sepal, petal, dorsal sepal. F,G. Column with pollinarium in place. F. Ventral view. G. Dorsal view. H,I. Pollinarium. H. Ventral view. I. Dorsal view (Singer 2006/21).