Vegetative anatomy and affinities of Dirachma socotrana (Dirachmaceae)

Stem and leaf anatomy of Dirachma socotrana, an endemic species from Socotr a, is described in detail. The diffuse porous to semi-ring-porous wood is c haracterized by solitary vessels and vessels in short radial multiples with a tendency for oblique/radial vessel arrangement, simple vessel perforatio ns, vascular tracheids, nonseptate fibers with simple to minutely bordered pits mainly confined to radial walls, axial parenchyma which is scanty para tracheal and in 1-2-seriate marginal bands, and mainly 1-2-seriate heteroce llular rays. The inner bark shows stratified fiber groups; the outer bark h as flaring rays. The dorsi-ventral leaves typically have an indumentum of s mall, unicellular hairs, anomocytic slomata, an adaxial epidermis largely c omposed of periclinally divided mucilage cells. The petiole and midrib vasc ular bundle is typically composed of a simple are-shaped strand. Prismatic crystals are common in the wood, bark, pith, and leaf. The systematic posit ion of the monotypic family Dirachmaceae in a newly defined Resales sensu A ngiosperm Phylogeny Group was established recently on the basis of molecula r data and confirmed by ovule and seed characters. Vegetative anatomical fe atures provide additional arguments for a placement of the family within th is order, particularly close to the Rhamnaceae.