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1 April 2001 Vegetative Anatomy and Affinities of Dirachma socotrana (Dirachmaceae)
Pieter Baas, Steven Jansen, Erik Smets
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Stem and leaf anatomy of Dirachma socotrana, an endemic species from Socotra, is described in detail. The diffuse porous to semi-ring-porous wood is characterized by solitary vessels and vessels in short radial multiples with a tendency for oblique/radial vessel arrangement, simple vessel perforations, vascular tracheids, nonseptate fibers with simple to minutely bordered pits mainly confined to radial walls, axial parenchyma which is scanty paratracheal and in 1–2-seriate marginal bands, and mainly 1–2-seriate heterocellular rays. The inner bark shows stratified fiber groups; the outer bark has flaring rays. The dorsiventral leaves typically have an indumentum of small, unicellular hairs, anomocytic stomata, an adaxial epidermis largely composed of periclinally divided mucilage cells. The petiole and midrib vascular bundle is typically composed of a simple arc-shaped strand. Prismatic crystals are common in the wood, bark, pith, and leaf. The systematic position of the monotypic family Dirachmaceae in a newly defined Rosales sensu Angiosperm Phylogeny Group was established recently on the basis of molecular data and confirmed by ovule and seed characters. Vegetative anatomical features provide additional arguments for a placement of the family within this order, particularly close to the Rhamnaceae.

Communicating Editor: Paul Wilson

Pieter Baas, Steven Jansen, and Erik Smets "Vegetative Anatomy and Affinities of Dirachma socotrana (Dirachmaceae)," Systematic Botany 26(2), 231-241, (1 April 2001).
Published: 1 April 2001
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