Barbacenia nana L. B. Sm. & Ayensu

Barbacenia nana L. B. Smith & Ayensu

SPECIMENS EXAMINED.—L. B. Smith and Ayensu 15973.

SURFACE VIEW.—Hairs: present on adaxial and abaxial surfaces; long and multicellular. Epidermis: adaxial cells square; thin walled. Abaxial cells square to rectangular; thin walled. Stomata: tetracytic, 21 × 18 μm; present on abaxial surface.

TRANSVERSE SECTION OF LAMINA.—Dorsiventral; V-shaped with margins turned slightly inversely. Adaxial and abaxial surfaces only slightly undulating; both surfaces covered with hairs. Epidermis: adaxial cells dome shaped to conical; thin walled. Abaxial cells more rounded to dome shaped; thin walled. Subjacent to adaxial epidermis is a distinct layer of parenchyma cells. Cuticle: thin and ridged on adaxial and abaxial surfaces. Stomata: present on abaxial surface; substomatal chamber present; usually flush with or slightly above epidermal surface. Mesophyll: two to three layers of palisade cells grading into a loosely arranged spongy tissue. Large number of translucent cells in spongy tissue, especially in midvein region. Vascular bundles: 44; few commissural bundles observed. One to two large vessels present in each vascular bundle,

mostly one. Two phloem units lying in flanges of wide Y-shaped abaxial girder. Inverted Y-shaped adaxial girder present on each vascular bundle; sometimes appearing T-shaped near adaxial surface. Some sclerenchyma strands observed on adaxial side of lamina replacing some palisade cells. Bundle sheath completely surrounding each vascular bundle. Crystals and tannins: none observed.