SEM Studies on Vessels in Ferns. 4. Astrolepis

By means of scanning electron microscopy, the nature of vessels is described for roots and rhizomes of Astrolepis sinuata (Lag. ex Swartz) D.M. Benham & Windham [= Notholaena sinuata (Lag. ex Swartz) Kaulf.], commonly placed in Pteridaceae. In both roots and rhizomes, end walls are variously distinct from lateral walls; a few perforation plates are quite elongate with numerous bars, but most are of medium or short length with fewer bars. Pit membrane remnants are generally sparse in the perforation plates. Lateral wall perforation plates are present; some may represent a multiplicity of facets at the tip of a tracheary element. Lateral walls may have intact pit membranes or perforations. No tracheids were identified; apparently all tracheary elements are vessel elements. The abundance of relatively short end walls with few bars on perforation plates may be correlated with rapid rates of water conduction during the short growing season of this fern, which occupies outcrops in arid parts of the southwestern United States and Mexico.