Anatomical Studies of the Neotropical Cyatheaceae. I. Alsophila and Nephelea

Abstract

The taxonomic treatment of the Cyatheaceae has undergone numerous revisions as summarized in previous studies (Tryon, 1970; Gastony, 1973; Lucansky, 1974). Earlier research has shown the taxonomic importance of anatomy and morphology to the study of this group of ferns (Holttum & Sen, 1961; Sen, 1964; Lucansky, 1974; Lucansky & White, 1974). Yet, despite this renewal of interest in the tree ferns, comparative anatomical data are almost totally lacking for the neotropical species. Tryon's (1970) revised classification of the Cyatheaceae recognizes three basic evolutionary lines among the squamate genera, based upon petiole scale characters. The genera Alsophila and Nephelea, with structurally marginate petiole scales having dark apical setae, constitute one evolutionary line. Similarities in the sporogenetic pattern, spore morphology, basal pinna structure, and potential for squaminate spine development also demonstrate a close phyletic relationship between these two genera (Gastony, 1973, p. 83). An attempt is made to determine whether the proposed phyletic relationship betweenA Isophila and Nephelea is supported by anatomical data. Our knowledge of anatomical data for the New World tree ferns is also increased. The following species were used in this study: Alsophila salvinii Hook., A. engelii Tryon, Nephelea erinacea (Karst.) Tryon var. erinacea, and N. polystichoides (Christ) Tryon. Voucher specimens are on file in the herbarium of Duke University. Developing shoot tips were collected in the moist, tropical, mountainous regions of Costa Rica and Venezuela. The plant materials were killed and fixed in formalin-acetic acid-alcohol (FAA) and sectioned on a macrotome (Lucansky, 1976b). The sections (slices) were partitioned into manageable sizes, dehydrated in a tertiary-butyl alcohol series, and embedded in paraffin (Johansen, 1940). Sections (8 um) were made and stained with safranin-fast green. Parts of stained sections were photographed with a 35 mm Zeiss C35 camera, whereas entire sections (slices) were photographed with a 35 mm single-lens reflex camera.