Systematic Anatomy of Cyclanthaceae (Monocotyledoneae)-An Overview

Abstract

A recent survey of lamina and stem anatomy of Cyclanthaceae, including information from species that represent ca. 25% of the family, allows a comparison with Pandanaceae and Palmae, which have putative affinities with the Cyclanthaceae. The three families are readily distinguished by a number of discrete morphological and anatomical features. We present synopses and diagnostic keys with special emphasis on lamina anatomy. The subdivision of the Cyclanthaceae proposed by Harling is supported by anatomical evidence, but, because of anatomical similarities, related genera may not always be clearly separated solely by lamina anatomy. The Palmae are especially isolated. Their distinctive features include a closed tubular leaf base, silica bodies in specialized cells (stegmata), exclusively simple stem vascular bundles, and vessels (sometimes with simple perforation plates) in stem, leaf, and root. Pandanaceae are distinguished, among other features, by cubical crystal bodies, an open leaf base, compound stem bundles without basipetal fusion, and possible lack of vessels in stem and leaf. Cyclanthaceae have an open leaf sheath but lack both silica bodies and cubical crystals, and commonly have mucilage cavities and diverse structural features (laticifers, styloids, parenchyma-like dead cells, tannin-like star figures) that, however, are not ubiquitous. In stems, vessels with long scalariform perforation plates occur in Thoracocarpus. Compound stem bundles show basipetal fusion of a distinctive kind. Sympodial branching below a terminal inflorescence occurs in some Cyclanthaceae and especially in the Pandanaceae, but never in the Palmae. In contrast, features by which these three families are traditionally associated seem superficial.