Anatomical Studies of the Neotropical Cyatheaceae. II. Metaxya and Lophosoria

Abstract

The classification of the monotypic tree fern genera Metaxya and Lophosoria has undergone several revisions. Early taxonomists placed these genera, with the dicksonioid group, in the family Cyatheaceae (Diels, 1902; Christensen, 1906; Maxon, 1912). Bower (1926) stressed the importance of soral position and placed these primitive genera in the family Protocyatheaceae. Later workers (Christensen, 1938; Copeland, 1947) included the two genera in the Cyatheaceae, but excluded the dicksonioid group from that family. Based upon morphological, developmental and anatomical data, Holttum and Sen (1961) again placed Metaxya and Lophosoria and the dicksonioid ferns into the single family Cyatheaceae. More recently, Tryon (1970) revised the classification of the Cyatheaceae, excluding members of the Dicksoniaceae. He recognized Metaxya and Lophosoria as distinctive genera and placed them in an independent position at the base of his phyletic scheme for the family. In this study, the anatomy of Metaxya rostrata (H.B.K.) Presl and Lophosoria quadripinnata (Gmel.) C. Chr. is elucidated and an attempt is made to determine whether the proposed phyletic relationship between these two taxa and the squamate genera of tree ferns is supported by anatomical data. Developing shoot tips of M. rostrata and L. quadripinnata were collected in montane and lowland rainforests in Costa Rica. The plant materials were killed and fixed in formalin-acetic acid-alcohol (FAA) and sectioned on a macrotome (Lucansky, 1976a). The slices were partitioned into manageable sizes, dehydrated in a tertiary-butyl alcohol series and embedded in paraffin (Johansen, 1940). Sections (10 f(m) were made and stained in a safranin-fast green series. Stained sections were photographed with a Nikon M-35S camera, whereas entire slices were photographed with a Pentax 35 mm single lens reflex camera. Voucher specimens are deposited in the herbarium of Duke University.