Barbacenia delicatula L. B. Sm. & Ayensu

Barbacenia delicatula L. B. Smith & Ayensu

SPECIMENS EXAMINED.—L. B. Smith and Ayensu 15975.

SURFACE VIEW.—Hairs: none present. Epidermis: adaxial cells mostly rectangular, few square and rounded; thin walled. Abaxial cells rectangular; thin walled. Stomata: paracytic, 15 × 16 μm; present on abaxial surface.

TRANSVERSE SECTION OF LAMINA.—Isolateral; V-shaped; margins of lamina turned slightly inversely. Adaxial and abaxial surfaces uniformly smooth with slight grooves separating each vascular bundle. Epidermis: adaxial cells rounded to dome shaped; thick walled. Abaxial cells rounded; thin walled. Subjacent to adaxial epidermis is a distinct layer of parenchyma cells. Following parenchyma cell layer are clusters of sclerenchyma strands surrounded by one-layered parenchyma cells; usually occur above vascular bundles. Other smaller sclerenchyma strands observed. Cuticle: thin on both surfaces and slightly ridged. Stomata: present on abaxial surface; small substomatal chamber present; flush with surface but appearing in grooves. Mesophyll: spongy tissue uniformly arranged with some large translucent cells especially in midvein region as well as midportion of mesophyll. Vascular bundles: 27; many commissural bundle’s observed. One to two large vessels present in each vascular bundle, mostly one. Two phloem units lying laterally in flanges of Y-shaped abaxial girder. Adaxial cap strictly nonexistent. Each vascular bundle completely surrounded by a bundle sheath. Crystals and tannins: none observed.

NOTE: This species is anatomically unique because of the lack of direct contact of sclerenchyma adaxial cap on the vascular bundles. The sclerenchyma caps that appear above the vascular bundles are separated by two to four layers of mesophyll cells.