SEM Studies on Vessels in Ferns. 16. Pacific Tree Ferns (Blechnaceae, Cyatheaceae, Dicksoniaceae)

Abstract

Scanning electron microscope (SEM) studies of tracheary elements of one species each of Sadleria (Blechnaceae), Alsophila (Cyatheaceae), Cibotium, and Dicksonia (Dicksoniaceae) showed that metaxylem of both roots and stems contains vessels with scalariform lateral wall pitting and scalariform perforation plates in which perforations are like lateral wall pits in size and shape. In Cyatheaceae and Dicksoniaceae, rhizome tracheary elements are short, contorted, with numerous facets. Several end wall facets of any given tracheary element in all genera studied can be perforation plates. At upper and lower ends of perforation plates, perforations have pit membrane remnants that contain porosities of various sizes, from large (nearly as big as the perforation) to extremely small (at the limit of resolution); the porosities are mostly circular in outline. No tracheids were observed with certainty. All tree ferns studied lack modifications of perforation plates like those of xeric ferns. The rhizome tracheary elements of Cyatheaceae are like those of Dicksoniaceae, but fusiform tracheary elements like those of many fern families occur in Sadleria (Blechnaceae); this correlates with the close grouping of Cyatheaceae with Dicksoniaceae in recent phylogenies that show Blechnaceae well removed from the tree fern families Cyatheaceae and Dicksoniaceae.