Barbacenia williamsii L. B. Sm.

Barbacenia williamsii L. B. Smith

SPECIMENS EXAMINED.—Dueke s.n.; Williams and Assis 6386; Pereira 2460–Pabst 3296.

SURFACE VIEW.—Hairs: absent. Epidermis: adaxial cells square to rectangular; abaxial cells more rounded. Walls thin on both surfaces. Stomata: paracytic, 18 × 12 μm; present on abaxial and adaxial surfaces.

TRANSVERSE SECTION OF LAMINA.—Isolateral; V-shaped. Adaxial and abaxial surfaces only slightly undulating. Epidermis: rounded to dome-shaped cells on abaxial and adaxial surfaces; few conical abaxial cells. Cells thin walled on both surfaces. Layer of parenchyma cells subjacent to epidermis. Cuticle: thin on adaxial and abaxial surfaces; slightly thicker on midvein. Stomata: present on abaxial and adaxial surfaces; small substomatal chamber present; flush with epidermal surface. Mesophyll: undifferentiated, spongy tissue compactly arranged. Two to three layers of large translucent palisade cells arranged radially above midvein. Some translucent cells present in midportion of spongy tissue. Vascular bundles: 33–49; commissural bundles few. One large vessel present in each vascular bundle. Two phloem units arranged laterally in flanges of Y-shaped abaxial girder. Inverted Y-shaped adaxial girder on each vascular bundle. Bundle sheath completely surrounding each vascular bundle. Crystals: none observed. Tannins: numerous, mostly in mesophyll.

Subkey III

Barbacenia williamsii L. B. Smith

Barbacenia williamsii L. B. Smith, Contr. U.S. Nat. Herb., 35:278, pl. 10: figs. 23, 24, 1962.—Ayensu, Smithsonian Contr. Bot., 15:61, fig. 22d–f, pl. 40b–d, 1974.

TYPE.—On iron ore, Serra da Mutuca, Mun. Nova Lima, Minas Gerais, Brazil, 1200–1400 m alt, 7 April 1945, Williams & Assis 6696 (GH, holotype; US, isotype).

DISTRIBUTION.—Brazil: Minas Gerais: Serra do Curral and Serra da Mutuca in Nova Lima.