Variation in Costa Rican Ophioglossum palmatum and Nomenclature of the Species

Abstract

In establishing the monotypic genus Cheiroglossa, Presl (1845, p. 57) segregated Ophioglossum palmatum on the following basis: Differt ab Ophioglosso habitu, reticulo venarum simplici, ortu spicarum plurium e margine frondis, ab Ophiodermate fronde revera stipitata, venulis secundariis intra maculas et ad maculas marginales liberis, spicis pluribus ad basim frondis marginalibus. Presl (1845, p. 56) also accepted the epiphytic and monotypic genus Ophioderma (Blume) Endl., which differs from Ophioglossum sensu stricto and from Cheiroglossa in having fronds that are narrow, strap-shaped, and entire or rarely forked at the apex, and in the median, basal position of a single or a pair of fertile segments: Sed Ophioderma ab Ophioglosso revera differt non solum habitu frondis fasciaeformi, sed praesertim venarum maculis simplicibus, venulis liberis nullis, exortu laterali spicae e vena media frondis. In the Index Filicum Christensen recognized neither segregate; Nakai (1925) rejected Cheiroglossa as a genus but upheld Ophioderma; Clausen (1938, p. 111) considered Cheiroglossa and Ophioderma to be subgenera of Ophioglossum; and Copeland (1947, p. 11) also submerged both into that genus, stating that a number of species are intermediate and link the three genera. Although there may be no cytological differences (Ninan, 1958), there are a number of morphological and anatomical reasons for separation at the subgeneric level (Chrysler, 1941; Nishida, 1952; Clausen, 1954, pp. 496-498; Maroti, 1965; van Cotthem, 1973). Several species and varieties have been proposed in subg. Cheiroglossa. Cheiroglossa malgassica (C. Chr.) Pic. Ser., from Madagascar, Reunion, and the Seychelles Islands, differs from typical 0. palmatum in having smaller fronds and areoles, in the fertile segments mostly inserted near the base of the sterile blade, and in a less deeply incised and thicker lamina and uniformly thick veins. Cheiroglossa louisii (Taton) Pic. Ser., from the Congo, has dichotomously segmented fronds with very long, narrow segments, hexagonal, elongate areoles with few included veinlets, and the fertile segments sometimes furcate. Only two collections are known of this species. Cheiroglossa austrobrasiliensis Brade, from Brazil, differs in lamina dimensions and color of the sterile segment and common petiole. It has narrow areoles, and the fertile segments are inserted both on the petiole and on the margins of the sterile segment. The present study is based on six large clumps of 0. palmatum collected at San Rafael de Vara Blanca, Province of Heredia, at 2000 m altitude. The plants grew as epiphytes on various trees, mostly Quercus sp. and Magnolia poasana Standl., together with other epiphytes, including Orchidaceae, Bromeliaceae, Araceae, and bryophytes. The area is a montane cloud forest, with rainfall averaging 3000 mm/year and temperatures 18?C. Voucher specimens are: Wagner & Gomez 1181 (CR), Lent 1615 (F), and Gomez 5070 (CR), and totalled 57 fertile fronds.