Origins and nature of vessels in monocotyledons. 3. Lowiaceae, with comments on rhizome anatomy

Sections and macerations of roots and stems of Orchidantha maxillarioides (Ridl.) K. Schum. (Lowiaceae) were examined with a scanning electron microscope (SEM). Vessels with long scalariform perforation plates occur in both roots and rhizome; perforation plates have more pit membrane remnants in rhizomes. At least a few tracheids are present. The degree of perforation plate specialization correlates with the moist forest understory habit of Orchidantha, and is similar to that in primitive families of monocotyledons that occupy marshy habitats. Vessel data suggest a primitive position for Lowiaceae within Zingiberales in accordance with recent phylogenies of monocotyledons, but recent molecular data point to a position more nearly terminal in the clade; this situation needs resolution. Raphides are figured with SEM, as are starch grains with rounded outlines, the shape of the latter newly reported for Lowiaceae.