Pollen grain morphology has been widely used in the classification of the Acanthaceae, where external pollen wall features have proved useful in determining relationships between taxa. Although detailed information has been accumulated using light microscopy, transmission electron microscopy and scanning electron microscopy (SEM) techniques, internal pollen wall features lack investigation and the techniques are cumbersome. A new technique involving precise cross sectioning or slicing of pollen grains at a selected position for examining wall ultrastructure, using a focused ion beam-scanning electron microscope (FIB-SEM), has been explored and promising results have been obtained. The FIB-SEM offers a good technique for reliable, high resolution, three-dimensional (3D) viewing of the internal structure of the pollen grain wall.

A new species, Rhinacanthus flavovirens Amarasinghe & Wijesundara (Acanthaceae), from Sri Lanka, is described and illustrated. It is compared with the closely allied Rhinacanthus nasutus and R. polonnaruwensis. A key to Rhinacanthus species in Sri Lanka is also presented.

Associational resistance occurs when host plants experience reduced attack when in the presence of other plant species (Atsatt & O'Dowd 1976, Tahvanainen & Root 1972). The issue is most studied in agriculture and forestry because of the potential benefits to pest control (Andow 1991, Brown & Ewel 1987, Tahvanainen & Root 1972), but recent research indicates that associational resistance may be relatively common in natural systems as well (Hjältén et al. 1993, Karban 2007, Vehviläinen et al. 2007, Wise et al. 2009; but see Östergård & Ehrlén 2005, White & Whitham 2000), especially against specialist herbivores (Hambäck et al. 2000, 2003; Stenberg et al. 2007).

A new species of Barleria (Acanthaceae), Barleria samhanensis Knees, A.G.Mill. & A.Patzelt, is described from southern Oman and a provisional assessment of its conservation status is provided. Further support is given for the recognition of the summit of Jabal Samhan as a distinct floristic unit.